diff options
Diffstat (limited to 'kernel/rcutree.c')
| -rw-r--r-- | kernel/rcutree.c | 3314 |
1 files changed, 0 insertions, 3314 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c deleted file mode 100644 index 32618b3fe4e6..000000000000 --- a/kernel/rcutree.c +++ /dev/null @@ -1,3314 +0,0 @@ -/* - * Read-Copy Update mechanism for mutual exclusion - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright IBM Corporation, 2008 - * - * Authors: Dipankar Sarma <dipankar@in.ibm.com> - * Manfred Spraul <manfred@colorfullife.com> - * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version - * - * Based on the original work by Paul McKenney <paulmck@us.ibm.com> - * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU - */ -#include <linux/types.h> -#include <linux/kernel.h> -#include <linux/init.h> -#include <linux/spinlock.h> -#include <linux/smp.h> -#include <linux/rcupdate.h> -#include <linux/interrupt.h> -#include <linux/sched.h> -#include <linux/nmi.h> -#include <linux/atomic.h> -#include <linux/bitops.h> -#include <linux/export.h> -#include <linux/completion.h> -#include <linux/moduleparam.h> -#include <linux/percpu.h> -#include <linux/notifier.h> -#include <linux/cpu.h> -#include <linux/mutex.h> -#include <linux/time.h> -#include <linux/kernel_stat.h> -#include <linux/wait.h> -#include <linux/kthread.h> -#include <linux/prefetch.h> -#include <linux/delay.h> -#include <linux/stop_machine.h> -#include <linux/random.h> -#include <linux/ftrace_event.h> -#include <linux/suspend.h> - -#include "rcutree.h" -#include <trace/events/rcu.h> - -#include "rcu.h" - -/* - * Strings used in tracepoints need to be exported via the - * tracing system such that tools like perf and trace-cmd can - * translate the string address pointers to actual text. - */ -#define TPS(x) tracepoint_string(x) - -/* Data structures. */ - -static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; -static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; - -/* - * In order to export the rcu_state name to the tracing tools, it - * needs to be added in the __tracepoint_string section. - * This requires defining a separate variable tp_<sname>_varname - * that points to the string being used, and this will allow - * the tracing userspace tools to be able to decipher the string - * address to the matching string. - */ -#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ -static char sname##_varname[] = #sname; \ -static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; \ -struct rcu_state sname##_state = { \ - .level = { &sname##_state.node[0] }, \ - .call = cr, \ - .fqs_state = RCU_GP_IDLE, \ - .gpnum = 0UL - 300UL, \ - .completed = 0UL - 300UL, \ - .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \ - .orphan_nxttail = &sname##_state.orphan_nxtlist, \ - .orphan_donetail = &sname##_state.orphan_donelist, \ - .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ - .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \ - .name = sname##_varname, \ - .abbr = sabbr, \ -}; \ -DEFINE_PER_CPU(struct rcu_data, sname##_data) - -RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); -RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); - -static struct rcu_state *rcu_state; -LIST_HEAD(rcu_struct_flavors); - -/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ -static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; -module_param(rcu_fanout_leaf, int, 0444); -int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; -static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ - NUM_RCU_LVL_0, - NUM_RCU_LVL_1, - NUM_RCU_LVL_2, - NUM_RCU_LVL_3, - NUM_RCU_LVL_4, -}; -int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ - -/* - * The rcu_scheduler_active variable transitions from zero to one just - * before the first task is spawned. So when this variable is zero, RCU - * can assume that there is but one task, allowing RCU to (for example) - * optimize synchronize_sched() to a simple barrier(). When this variable - * is one, RCU must actually do all the hard work required to detect real - * grace periods. This variable is also used to suppress boot-time false - * positives from lockdep-RCU error checking. - */ -int rcu_scheduler_active __read_mostly; -EXPORT_SYMBOL_GPL(rcu_scheduler_active); - -/* - * The rcu_scheduler_fully_active variable transitions from zero to one - * during the early_initcall() processing, which is after the scheduler - * is capable of creating new tasks. So RCU processing (for example, - * creating tasks for RCU priority boosting) must be delayed until after - * rcu_scheduler_fully_active transitions from zero to one. We also - * currently delay invocation of any RCU callbacks until after this point. - * - * It might later prove better for people registering RCU callbacks during - * early boot to take responsibility for these callbacks, but one step at - * a time. - */ -static int rcu_scheduler_fully_active __read_mostly; - -#ifdef CONFIG_RCU_BOOST - -/* - * Control variables for per-CPU and per-rcu_node kthreads. These - * handle all flavors of RCU. - */ -static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); -DEFINE_PER_CPU(char, rcu_cpu_has_work); - -#endif /* #ifdef CONFIG_RCU_BOOST */ - -static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); -static void invoke_rcu_core(void); -static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); - -/* - * Track the rcutorture test sequence number and the update version - * number within a given test. The rcutorture_testseq is incremented - * on every rcutorture module load and unload, so has an odd value - * when a test is running. The rcutorture_vernum is set to zero - * when rcutorture starts and is incremented on each rcutorture update. - * These variables enable correlating rcutorture output with the - * RCU tracing information. - */ -unsigned long rcutorture_testseq; -unsigned long rcutorture_vernum; - -/* - * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s - * permit this function to be invoked without holding the root rcu_node - * structure's ->lock, but of course results can be subject to change. - */ -static int rcu_gp_in_progress(struct rcu_state *rsp) -{ - return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); -} - -/* - * Note a quiescent state. Because we do not need to know - * how many quiescent states passed, just if there was at least - * one since the start of the grace period, this just sets a flag. - * The caller must have disabled preemption. - */ -void rcu_sched_qs(int cpu) -{ - struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); - - if (rdp->passed_quiesce == 0) - trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs")); - rdp->passed_quiesce = 1; -} - -void rcu_bh_qs(int cpu) -{ - struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); - - if (rdp->passed_quiesce == 0) - trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs")); - rdp->passed_quiesce = 1; -} - -/* - * Note a context switch. This is a quiescent state for RCU-sched, - * and requires special handling for preemptible RCU. - * The caller must have disabled preemption. - */ -void rcu_note_context_switch(int cpu) -{ - trace_rcu_utilization(TPS("Start context switch")); - rcu_sched_qs(cpu); - rcu_preempt_note_context_switch(cpu); - trace_rcu_utilization(TPS("End context switch")); -} -EXPORT_SYMBOL_GPL(rcu_note_context_switch); - -DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { - .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, - .dynticks = ATOMIC_INIT(1), -#ifdef CONFIG_NO_HZ_FULL_SYSIDLE - .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE, - .dynticks_idle = ATOMIC_INIT(1), -#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ -}; - -static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */ -static long qhimark = 10000; /* If this many pending, ignore blimit. */ -static long qlowmark = 100; /* Once only this many pending, use blimit. */ - -module_param(blimit, long, 0444); -module_param(qhimark, long, 0444); -module_param(qlowmark, long, 0444); - -static ulong jiffies_till_first_fqs = ULONG_MAX; -static ulong jiffies_till_next_fqs = ULONG_MAX; - -module_param(jiffies_till_first_fqs, ulong, 0644); -module_param(jiffies_till_next_fqs, ulong, 0644); - -static void rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp); -static void force_qs_rnp(struct rcu_state *rsp, - int (*f)(struct rcu_data *rsp, bool *isidle, - unsigned long *maxj), - bool *isidle, unsigned long *maxj); -static void force_quiescent_state(struct rcu_state *rsp); -static int rcu_pending(int cpu); - -/* - * Return the number of RCU-sched batches processed thus far for debug & stats. - */ -long rcu_batches_completed_sched(void) -{ - return rcu_sched_state.completed; -} -EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); - -/* - * Return the number of RCU BH batches processed thus far for debug & stats. - */ -long rcu_batches_completed_bh(void) -{ - return rcu_bh_state.completed; -} -EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); - -/* - * Force a quiescent state for RCU BH. - */ -void rcu_bh_force_quiescent_state(void) -{ - force_quiescent_state(&rcu_bh_state); -} -EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); - -/* - * Record the number of times rcutorture tests have been initiated and - * terminated. This information allows the debugfs tracing stats to be - * correlated to the rcutorture messages, even when the rcutorture module - * is being repeatedly loaded and unloaded. In other words, we cannot - * store this state in rcutorture itself. - */ -void rcutorture_record_test_transition(void) -{ - rcutorture_testseq++; - rcutorture_vernum = 0; -} -EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); - -/* - * Record the number of writer passes through the current rcutorture test. - * This is also used to correlate debugfs tracing stats with the rcutorture - * messages. - */ -void rcutorture_record_progress(unsigned long vernum) -{ - rcutorture_vernum++; -} -EXPORT_SYMBOL_GPL(rcutorture_record_progress); - -/* - * Force a quiescent state for RCU-sched. - */ -void rcu_sched_force_quiescent_state(void) -{ - force_quiescent_state(&rcu_sched_state); -} -EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); - -/* - * Does the CPU have callbacks ready to be invoked? - */ -static int -cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) -{ - return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] && - rdp->nxttail[RCU_DONE_TAIL] != NULL; -} - -/* - * Does the current CPU require a not-yet-started grace period? - * The caller must have disabled interrupts to prevent races with - * normal callback registry. - */ -static int -cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) -{ - int i; - - if (rcu_gp_in_progress(rsp)) - return 0; /* No, a grace period is already in progress. */ - if (rcu_nocb_needs_gp(rsp)) - return 1; /* Yes, a no-CBs CPU needs one. */ - if (!rdp->nxttail[RCU_NEXT_TAIL]) - return 0; /* No, this is a no-CBs (or offline) CPU. */ - if (*rdp->nxttail[RCU_NEXT_READY_TAIL]) - return 1; /* Yes, this CPU has newly registered callbacks. */ - for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) - if (rdp->nxttail[i - 1] != rdp->nxttail[i] && - ULONG_CMP_LT(ACCESS_ONCE(rsp->completed), - rdp->nxtcompleted[i])) - return 1; /* Yes, CBs for future grace period. */ - return 0; /* No grace period needed. */ -} - -/* - * Return the root node of the specified rcu_state structure. - */ -static struct rcu_node *rcu_get_root(struct rcu_state *rsp) -{ - return &rsp->node[0]; -} - -/* - * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state - * - * If the new value of the ->dynticks_nesting counter now is zero, - * we really have entered idle, and must do the appropriate accounting. - * The caller must have disabled interrupts. - */ -static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval, - bool user) -{ - trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting); - if (!user && !is_idle_task(current)) { - struct task_struct *idle = idle_task(smp_processor_id()); - - trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0); - ftrace_dump(DUMP_ORIG); - WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", - current->pid, current->comm, - idle->pid, idle->comm); /* must be idle task! */ - } - rcu_prepare_for_idle(smp_processor_id()); - /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ - smp_mb__before_atomic_inc(); /* See above. */ - atomic_inc(&rdtp->dynticks); - smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ - WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); - - /* - * It is illegal to enter an extended quiescent state while - * in an RCU read-side critical section. - */ - rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), - "Illegal idle entry in RCU read-side critical section."); - rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), - "Illegal idle entry in RCU-bh read-side critical section."); - rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), - "Illegal idle entry in RCU-sched read-side critical section."); -} - -/* - * Enter an RCU extended quiescent state, which can be either the - * idle loop or adaptive-tickless usermode execution. - */ -static void rcu_eqs_enter(bool user) -{ - long long oldval; - struct rcu_dynticks *rdtp; - - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); - if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) - rdtp->dynticks_nesting = 0; - else - rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; - rcu_eqs_enter_common(rdtp, oldval, user); -} - -/** - * rcu_idle_enter - inform RCU that current CPU is entering idle - * - * Enter idle mode, in other words, -leave- the mode in which RCU - * read-side critical sections can occur. (Though RCU read-side - * critical sections can occur in irq handlers in idle, a possibility - * handled by irq_enter() and irq_exit().) - * - * We crowbar the ->dynticks_nesting field to zero to allow for - * the possibility of usermode upcalls having messed up our count - * of interrupt nesting level during the prior busy period. - */ -void rcu_idle_enter(void) -{ - unsigned long flags; - - local_irq_save(flags); - rcu_eqs_enter(false); - rcu_sysidle_enter(&__get_cpu_var(rcu_dynticks), 0); - local_irq_restore(flags); -} -EXPORT_SYMBOL_GPL(rcu_idle_enter); - -#ifdef CONFIG_RCU_USER_QS -/** - * rcu_user_enter - inform RCU that we are resuming userspace. - * - * Enter RCU idle mode right before resuming userspace. No use of RCU - * is permitted between this call and rcu_user_exit(). This way the - * CPU doesn't need to maintain the tick for RCU maintenance purposes - * when the CPU runs in userspace. - */ -void rcu_user_enter(void) -{ - rcu_eqs_enter(1); -} -#endif /* CONFIG_RCU_USER_QS */ - -/** - * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle - * - * Exit from an interrupt handler, which might possibly result in entering - * idle mode, in other words, leaving the mode in which read-side critical - * sections can occur. - * - * This code assumes that the idle loop never does anything that might - * result in unbalanced calls to irq_enter() and irq_exit(). If your - * architecture violates this assumption, RCU will give you what you - * deserve, good and hard. But very infrequently and irreproducibly. - * - * Use things like work queues to work around this limitation. - * - * You have been warned. - */ -void rcu_irq_exit(void) -{ - unsigned long flags; - long long oldval; - struct rcu_dynticks *rdtp; - - local_irq_save(flags); - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - rdtp->dynticks_nesting--; - WARN_ON_ONCE(rdtp->dynticks_nesting < 0); - if (rdtp->dynticks_nesting) - trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting); - else - rcu_eqs_enter_common(rdtp, oldval, true); - rcu_sysidle_enter(rdtp, 1); - local_irq_restore(flags); -} - -/* - * rcu_eqs_exit_common - current CPU moving away from extended quiescent state - * - * If the new value of the ->dynticks_nesting counter was previously zero, - * we really have exited idle, and must do the appropriate accounting. - * The caller must have disabled interrupts. - */ -static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval, - int user) -{ - smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ - atomic_inc(&rdtp->dynticks); - /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ - smp_mb__after_atomic_inc(); /* See above. */ - WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); - rcu_cleanup_after_idle(smp_processor_id()); - trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting); - if (!user && !is_idle_task(current)) { - struct task_struct *idle = idle_task(smp_processor_id()); - - trace_rcu_dyntick(TPS("Error on exit: not idle task"), - oldval, rdtp->dynticks_nesting); - ftrace_dump(DUMP_ORIG); - WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", - current->pid, current->comm, - idle->pid, idle->comm); /* must be idle task! */ - } -} - -/* - * Exit an RCU extended quiescent state, which can be either the - * idle loop or adaptive-tickless usermode execution. - */ -static void rcu_eqs_exit(bool user) -{ - struct rcu_dynticks *rdtp; - long long oldval; - - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - WARN_ON_ONCE(oldval < 0); - if (oldval & DYNTICK_TASK_NEST_MASK) - rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; - else - rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; - rcu_eqs_exit_common(rdtp, oldval, user); -} - -/** - * rcu_idle_exit - inform RCU that current CPU is leaving idle - * - * Exit idle mode, in other words, -enter- the mode in which RCU - * read-side critical sections can occur. - * - * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to - * allow for the possibility of usermode upcalls messing up our count - * of interrupt nesting level during the busy period that is just - * now starting. - */ -void rcu_idle_exit(void) -{ - unsigned long flags; - - local_irq_save(flags); - rcu_eqs_exit(false); - rcu_sysidle_exit(&__get_cpu_var(rcu_dynticks), 0); - local_irq_restore(flags); -} -EXPORT_SYMBOL_GPL(rcu_idle_exit); - -#ifdef CONFIG_RCU_USER_QS -/** - * rcu_user_exit - inform RCU that we are exiting userspace. - * - * Exit RCU idle mode while entering the kernel because it can - * run a RCU read side critical section anytime. - */ -void rcu_user_exit(void) -{ - rcu_eqs_exit(1); -} -#endif /* CONFIG_RCU_USER_QS */ - -/** - * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle - * - * Enter an interrupt handler, which might possibly result in exiting - * idle mode, in other words, entering the mode in which read-side critical - * sections can occur. - * - * Note that the Linux kernel is fully capable of entering an interrupt - * handler that it never exits, for example when doing upcalls to - * user mode! This code assumes that the idle loop never does upcalls to - * user mode. If your architecture does do upcalls from the idle loop (or - * does anything else that results in unbalanced calls to the irq_enter() - * and irq_exit() functions), RCU will give you what you deserve, good - * and hard. But very infrequently and irreproducibly. - * - * Use things like work queues to work around this limitation. - * - * You have been warned. - */ -void rcu_irq_enter(void) -{ - unsigned long flags; - struct rcu_dynticks *rdtp; - long long oldval; - - local_irq_save(flags); - rdtp = &__get_cpu_var(rcu_dynticks); - oldval = rdtp->dynticks_nesting; - rdtp->dynticks_nesting++; - WARN_ON_ONCE(rdtp->dynticks_nesting == 0); - if (oldval) - trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting); - else - rcu_eqs_exit_common(rdtp, oldval, true); - rcu_sysidle_exit(rdtp, 1); - local_irq_restore(flags); -} - -/** - * rcu_nmi_enter - inform RCU of entry to NMI context - * - * If the CPU was idle with dynamic ticks active, and there is no - * irq handler running, this updates rdtp->dynticks_nmi to let the - * RCU grace-period handling know that the CPU is active. - */ -void rcu_nmi_enter(void) -{ - struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - - if (rdtp->dynticks_nmi_nesting == 0 && - (atomic_read(&rdtp->dynticks) & 0x1)) - return; - rdtp->dynticks_nmi_nesting++; - smp_mb__before_atomic_inc(); /* Force delay from prior write. */ - atomic_inc(&rdtp->dynticks); - /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ - smp_mb__after_atomic_inc(); /* See above. */ - WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); -} - -/** - * rcu_nmi_exit - inform RCU of exit from NMI context - * - * If the CPU was idle with dynamic ticks active, and there is no - * irq handler running, this updates rdtp->dynticks_nmi to let the - * RCU grace-period handling know that the CPU is no longer active. - */ -void rcu_nmi_exit(void) -{ - struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - - if (rdtp->dynticks_nmi_nesting == 0 || - --rdtp->dynticks_nmi_nesting != 0) - return; - /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ - smp_mb__before_atomic_inc(); /* See above. */ - atomic_inc(&rdtp->dynticks); - smp_mb__after_atomic_inc(); /* Force delay to next write. */ - WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); -} - -/** - * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle - * - * If the current CPU is in its idle loop and is neither in an interrupt - * or NMI handler, return true. - */ -int rcu_is_cpu_idle(void) -{ - int ret; - - preempt_disable(); - ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; - preempt_enable(); - return ret; -} -EXPORT_SYMBOL(rcu_is_cpu_idle); - -#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) - -/* - * Is the current CPU online? Disable preemption to avoid false positives - * that could otherwise happen due to the current CPU number being sampled, - * this task being preempted, its old CPU being taken offline, resuming - * on some other CPU, then determining that its old CPU is now offline. - * It is OK to use RCU on an offline processor during initial boot, hence - * the check for rcu_scheduler_fully_active. Note also that it is OK - * for a CPU coming online to use RCU for one jiffy prior to marking itself - * online in the cpu_online_mask. Similarly, it is OK for a CPU going - * offline to continue to use RCU for one jiffy after marking itself - * offline in the cpu_online_mask. This leniency is necessary given the - * non-atomic nature of the online and offline processing, for example, - * the fact that a CPU enters the scheduler after completing the CPU_DYING - * notifiers. - * - * This is also why RCU internally marks CPUs online during the - * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. - * - * Disable checking if in an NMI handler because we cannot safely report - * errors from NMI handlers anyway. - */ -bool rcu_lockdep_current_cpu_online(void) -{ - struct rcu_data *rdp; - struct rcu_node *rnp; - bool ret; - - if (in_nmi()) - return 1; - preempt_disable(); - rdp = &__get_cpu_var(rcu_sched_data); - rnp = rdp->mynode; - ret = (rdp->grpmask & rnp->qsmaskinit) || - !rcu_scheduler_fully_active; - preempt_enable(); - return ret; -} -EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); - -#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ - -/** - * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle - * - * If the current CPU is idle or running at a first-level (not nested) - * interrupt from idle, return true. The caller must have at least - * disabled preemption. - */ -static int rcu_is_cpu_rrupt_from_idle(void) -{ - return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; -} - -/* - * Snapshot the specified CPU's dynticks counter so that we can later - * credit them with an implicit quiescent state. Return 1 if this CPU - * is in dynticks idle mode, which is an extended quiescent state. - */ -static int dyntick_save_progress_counter(struct rcu_data *rdp, - bool *isidle, unsigned long *maxj) -{ - rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); - rcu_sysidle_check_cpu(rdp, isidle, maxj); - return (rdp->dynticks_snap & 0x1) == 0; -} - -/* - * Return true if the specified CPU has passed through a quiescent - * state by virtue of being in or having passed through an dynticks - * idle state since the last call to dyntick_save_progress_counter() - * for this same CPU, or by virtue of having been offline. - */ -static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, - bool *isidle, unsigned long *maxj) -{ - unsigned int curr; - unsigned int snap; - - curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); - snap = (unsigned int)rdp->dynticks_snap; - - /* - * If the CPU passed through or entered a dynticks idle phase with - * no active irq/NMI handlers, then we can safely pretend that the CPU - * already acknowledged the request to pass through a quiescent - * state. Either way, that CPU cannot possibly be in an RCU - * read-side critical section that started before the beginning - * of the current RCU grace period. - */ - if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { - trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); - rdp->dynticks_fqs++; - return 1; - } - - /* - * Check for the CPU being offline, but only if the grace period - * is old enough. We don't need to worry about the CPU changing - * state: If we see it offline even once, it has been through a - * quiescent state. - * - * The reason for insisting that the grace period be at least - * one jiffy old is that CPUs that are not quite online and that - * have just gone offline can still execute RCU read-side critical - * sections. - */ - if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies)) - return 0; /* Grace period is not old enough. */ - barrier(); - if (cpu_is_offline(rdp->cpu)) { - trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl")); - rdp->offline_fqs++; - return 1; - } - - /* - * There is a possibility that a CPU in adaptive-ticks state - * might run in the kernel with the scheduling-clock tick disabled - * for an extended time period. Invoke rcu_kick_nohz_cpu() to - * force the CPU to restart the scheduling-clock tick in this - * CPU is in this state. - */ - rcu_kick_nohz_cpu(rdp->cpu); - - return 0; -} - -static void record_gp_stall_check_time(struct rcu_state *rsp) -{ - rsp->gp_start = jiffies; - rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); -} - -/* - * Dump stacks of all tasks running on stalled CPUs. This is a fallback - * for architectures that do not implement trigger_all_cpu_backtrace(). - * The NMI-triggered stack traces are more accurate because they are - * printed by the target CPU. - */ -static void rcu_dump_cpu_stacks(struct rcu_state *rsp) -{ - int cpu; - unsigned long flags; - struct rcu_node *rnp; - - rcu_for_each_leaf_node(rsp, rnp) { - raw_spin_lock_irqsave(&rnp->lock, flags); - if (rnp->qsmask != 0) { - for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) - if (rnp->qsmask & (1UL << cpu)) - dump_cpu_task(rnp->grplo + cpu); - } - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } -} - -static void print_other_cpu_stall(struct rcu_state *rsp) -{ - int cpu; - long delta; - unsigned long flags; - int ndetected = 0; - struct rcu_node *rnp = rcu_get_root(rsp); - long totqlen = 0; - - /* Only let one CPU complain about others per time interval. */ - - raw_spin_lock_irqsave(&rnp->lock, flags); - delta = jiffies - rsp->jiffies_stall; - if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - - /* - * OK, time to rat on our buddy... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - pr_err("INFO: %s detected stalls on CPUs/tasks:", - rsp->name); - print_cpu_stall_info_begin(); - rcu_for_each_leaf_node(rsp, rnp) { - raw_spin_lock_irqsave(&rnp->lock, flags); - ndetected += rcu_print_task_stall(rnp); - if (rnp->qsmask != 0) { - for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) - if (rnp->qsmask & (1UL << cpu)) { - print_cpu_stall_info(rsp, - rnp->grplo + cpu); - ndetected++; - } - } - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } - - /* - * Now rat on any tasks that got kicked up to the root rcu_node - * due to CPU offlining. - */ - rnp = rcu_get_root(rsp); - raw_spin_lock_irqsave(&rnp->lock, flags); - ndetected += rcu_print_task_stall(rnp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); - - print_cpu_stall_info_end(); - for_each_possible_cpu(cpu) - totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; - pr_cont("(detected by %d, t=%ld jiffies, g=%lu, c=%lu, q=%lu)\n", - smp_processor_id(), (long)(jiffies - rsp->gp_start), - rsp->gpnum, rsp->completed, totqlen); - if (ndetected == 0) - pr_err("INFO: Stall ended before state dump start\n"); - else if (!trigger_all_cpu_backtrace()) - rcu_dump_cpu_stacks(rsp); - - /* Complain about tasks blocking the grace period. */ - - rcu_print_detail_task_stall(rsp); - - force_quiescent_state(rsp); /* Kick them all. */ -} - -static void print_cpu_stall(struct rcu_state *rsp) -{ - int cpu; - unsigned long flags; - struct rcu_node *rnp = rcu_get_root(rsp); - long totqlen = 0; - - /* - * OK, time to rat on ourselves... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - pr_err("INFO: %s self-detected stall on CPU", rsp->name); - print_cpu_stall_info_begin(); - print_cpu_stall_info(rsp, smp_processor_id()); - print_cpu_stall_info_end(); - for_each_possible_cpu(cpu) - totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; - pr_cont(" (t=%lu jiffies g=%lu c=%lu q=%lu)\n", - jiffies - rsp->gp_start, rsp->gpnum, rsp->completed, totqlen); - if (!trigger_all_cpu_backtrace()) - dump_stack(); - - raw_spin_lock_irqsave(&rnp->lock, flags); - if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) - rsp->jiffies_stall = jiffies + - 3 * rcu_jiffies_till_stall_check() + 3; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - - set_need_resched(); /* kick ourselves to get things going. */ -} - -static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long j; - unsigned long js; - struct rcu_node *rnp; - - if (rcu_cpu_stall_suppress) - return; - j = ACCESS_ONCE(jiffies); - js = ACCESS_ONCE(rsp->jiffies_stall); - rnp = rdp->mynode; - if (rcu_gp_in_progress(rsp) && - (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { - - /* We haven't checked in, so go dump stack. */ - print_cpu_stall(rsp); - - } else if (rcu_gp_in_progress(rsp) && - ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { - - /* They had a few time units to dump stack, so complain. */ - print_other_cpu_stall(rsp); - } -} - -/** - * rcu_cpu_stall_reset - prevent further stall warnings in current grace period - * - * Set the stall-warning timeout way off into the future, thus preventing - * any RCU CPU stall-warning messages from appearing in the current set of - * RCU grace periods. - * - * The caller must disable hard irqs. - */ -void rcu_cpu_stall_reset(void) -{ - struct rcu_state *rsp; - - for_each_rcu_flavor(rsp) - rsp->jiffies_stall = jiffies + ULONG_MAX / 2; -} - -/* - * Initialize the specified rcu_data structure's callback list to empty. - */ -static void init_callback_list(struct rcu_data *rdp) -{ - int i; - - if (init_nocb_callback_list(rdp)) - return; - rdp->nxtlist = NULL; - for (i = 0; i < RCU_NEXT_SIZE; i++) - rdp->nxttail[i] = &rdp->nxtlist; -} - -/* - * Determine the value that ->completed will have at the end of the - * next subsequent grace period. This is used to tag callbacks so that - * a CPU can invoke callbacks in a timely fashion even if that CPU has - * been dyntick-idle for an extended period with callbacks under the - * influence of RCU_FAST_NO_HZ. - * - * The caller must hold rnp->lock with interrupts disabled. - */ -static unsigned long rcu_cbs_completed(struct rcu_state *rsp, - struct rcu_node *rnp) -{ - /* - * If RCU is idle, we just wait for the next grace period. - * But we can only be sure that RCU is idle if we are looking - * at the root rcu_node structure -- otherwise, a new grace - * period might have started, but just not yet gotten around - * to initializing the current non-root rcu_node structure. - */ - if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed) - return rnp->completed + 1; - - /* - * Otherwise, wait for a possible partial grace period and - * then the subsequent full grace period. - */ - return rnp->completed + 2; -} - -/* - * Trace-event helper function for rcu_start_future_gp() and - * rcu_nocb_wait_gp(). - */ -static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, - unsigned long c, const char *s) -{ - trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, - rnp->completed, c, rnp->level, - rnp->grplo, rnp->grphi, s); -} - -/* - * Start some future grace period, as needed to handle newly arrived - * callbacks. The required future grace periods are recorded in each - * rcu_node structure's ->need_future_gp field. - * - * The caller must hold the specified rcu_node structure's ->lock. - */ -static unsigned long __maybe_unused -rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp) -{ - unsigned long c; - int i; - struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); - - /* - * Pick up grace-period number for new callbacks. If this - * grace period is already marked as needed, return to the caller. - */ - c = rcu_cbs_completed(rdp->rsp, rnp); - trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); - if (rnp->need_future_gp[c & 0x1]) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); - return c; - } - - /* - * If either this rcu_node structure or the root rcu_node structure - * believe that a grace period is in progress, then we must wait - * for the one following, which is in "c". Because our request - * will be noticed at the end of the current grace period, we don't - * need to explicitly start one. - */ - if (rnp->gpnum != rnp->completed || - ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) { - rnp->need_future_gp[c & 0x1]++; - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); - return c; - } - - /* - * There might be no grace period in progress. If we don't already - * hold it, acquire the root rcu_node structure's lock in order to - * start one (if needed). - */ - if (rnp != rnp_root) - raw_spin_lock(&rnp_root->lock); - - /* - * Get a new grace-period number. If there really is no grace - * period in progress, it will be smaller than the one we obtained - * earlier. Adjust callbacks as needed. Note that even no-CBs - * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed. - */ - c = rcu_cbs_completed(rdp->rsp, rnp_root); - for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++) - if (ULONG_CMP_LT(c, rdp->nxtcompleted[i])) - rdp->nxtcompleted[i] = c; - - /* - * If the needed for the required grace period is already - * recorded, trace and leave. - */ - if (rnp_root->need_future_gp[c & 0x1]) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); - goto unlock_out; - } - - /* Record the need for the future grace period. */ - rnp_root->need_future_gp[c & 0x1]++; - - /* If a grace period is not already in progress, start one. */ - if (rnp_root->gpnum != rnp_root->completed) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); - } else { - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); - rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); - } -unlock_out: - if (rnp != rnp_root) - raw_spin_unlock(&rnp_root->lock); - return c; -} - -/* - * Clean up any old requests for the just-ended grace period. Also return - * whether any additional grace periods have been requested. Also invoke - * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads - * waiting for this grace period to complete. - */ -static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) -{ - int c = rnp->completed; - int needmore; - struct rcu_data *rdp = this_cpu_ptr(rsp->rda); - - rcu_nocb_gp_cleanup(rsp, rnp); - rnp->need_future_gp[c & 0x1] = 0; - needmore = rnp->need_future_gp[(c + 1) & 0x1]; - trace_rcu_future_gp(rnp, rdp, c, - needmore ? TPS("CleanupMore") : TPS("Cleanup")); - return needmore; -} - -/* - * If there is room, assign a ->completed number to any callbacks on - * this CPU that have not already been assigned. Also accelerate any - * callbacks that were previously assigned a ->completed number that has - * since proven to be too conservative, which can happen if callbacks get - * assigned a ->completed number while RCU is idle, but with reference to - * a non-root rcu_node structure. This function is idempotent, so it does - * not hurt to call it repeatedly. - * - * The caller must hold rnp->lock with interrupts disabled. - */ -static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp) -{ - unsigned long c; - int i; - - /* If the CPU has no callbacks, nothing to do. */ - if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) - return; - - /* - * Starting from the sublist containing the callbacks most - * recently assigned a ->completed number and working down, find the - * first sublist that is not assignable to an upcoming grace period. - * Such a sublist has something in it (first two tests) and has - * a ->completed number assigned that will complete sooner than - * the ->completed number for newly arrived callbacks (last test). - * - * The key point is that any later sublist can be assigned the - * same ->completed number as the newly arrived callbacks, which - * means that the callbacks in any of these later sublist can be - * grouped into a single sublist, whether or not they have already - * been assigned a ->completed number. - */ - c = rcu_cbs_completed(rsp, rnp); - for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--) - if (rdp->nxttail[i] != rdp->nxttail[i - 1] && - !ULONG_CMP_GE(rdp->nxtcompleted[i], c)) - break; - - /* - * If there are no sublist for unassigned callbacks, leave. - * At the same time, advance "i" one sublist, so that "i" will - * index into the sublist where all the remaining callbacks should - * be grouped into. - */ - if (++i >= RCU_NEXT_TAIL) - return; - - /* - * Assign all subsequent callbacks' ->completed number to the next - * full grace period and group them all in the sublist initially - * indexed by "i". - */ - for (; i <= RCU_NEXT_TAIL; i++) { - rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL]; - rdp->nxtcompleted[i] = c; - } - /* Record any needed additional grace periods. */ - rcu_start_future_gp(rnp, rdp); - - /* Trace depending on how much we were able to accelerate. */ - if (!*rdp->nxttail[RCU_WAIT_TAIL]) - trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB")); - else - trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB")); -} - -/* - * Move any callbacks whose grace period has completed to the - * RCU_DONE_TAIL sublist, then compact the remaining sublists and - * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL - * sublist. This function is idempotent, so it does not hurt to - * invoke it repeatedly. As long as it is not invoked -too- often... - * - * The caller must hold rnp->lock with interrupts disabled. - */ -static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp) -{ - int i, j; - - /* If the CPU has no callbacks, nothing to do. */ - if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) - return; - - /* - * Find all callbacks whose ->completed numbers indicate that they - * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. - */ - for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) { - if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i])) - break; - rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i]; - } - /* Clean up any sublist tail pointers that were misordered above. */ - for (j = RCU_WAIT_TAIL; j < i; j++) - rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL]; - - /* Copy down callbacks to fill in empty sublists. */ - for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) { - if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL]) - break; - rdp->nxttail[j] = rdp->nxttail[i]; - rdp->nxtcompleted[j] = rdp->nxtcompleted[i]; - } - - /* Classify any remaining callbacks. */ - rcu_accelerate_cbs(rsp, rnp, rdp); -} - -/* - * Update CPU-local rcu_data state to record the beginnings and ends of - * grace periods. The caller must hold the ->lock of the leaf rcu_node - * structure corresponding to the current CPU, and must have irqs disabled. - */ -static void __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) -{ - /* Handle the ends of any preceding grace periods first. */ - if (rdp->completed == rnp->completed) { - - /* No grace period end, so just accelerate recent callbacks. */ - rcu_accelerate_cbs(rsp, rnp, rdp); - - } else { - - /* Advance callbacks. */ - rcu_advance_cbs(rsp, rnp, rdp); - - /* Remember that we saw this grace-period completion. */ - rdp->completed = rnp->completed; - trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend")); - } - - if (rdp->gpnum != rnp->gpnum) { - /* - * If the current grace period is waiting for this CPU, - * set up to detect a quiescent state, otherwise don't - * go looking for one. - */ - rdp->gpnum = rnp->gpnum; - trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart")); - rdp->passed_quiesce = 0; - rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask); - zero_cpu_stall_ticks(rdp); - } -} - -static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - struct rcu_node *rnp; - - local_irq_save(flags); - rnp = rdp->mynode; - if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) && - rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */ - !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ - local_irq_restore(flags); - return; - } - __note_gp_changes(rsp, rnp, rdp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -/* - * Initialize a new grace period. - */ -static int rcu_gp_init(struct rcu_state *rsp) -{ - struct rcu_data *rdp; - struct rcu_node *rnp = rcu_get_root(rsp); - - rcu_bind_gp_kthread(); - raw_spin_lock_irq(&rnp->lock); - rsp->gp_flags = 0; /* Clear all flags: New grace period. */ - - if (rcu_gp_in_progress(rsp)) { - /* Grace period already in progress, don't start another. */ - raw_spin_unlock_irq(&rnp->lock); - return 0; - } - - /* Advance to a new grace period and initialize state. */ - rsp->gpnum++; - trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start")); - record_gp_stall_check_time(rsp); - raw_spin_unlock_irq(&rnp->lock); - - /* Exclude any concurrent CPU-hotplug operations. */ - mutex_lock(&rsp->onoff_mutex); - - /* - * Set the quiescent-state-needed bits in all the rcu_node - * structures for all currently online CPUs in breadth-first order, - * starting from the root rcu_node structure, relying on the layout - * of the tree within the rsp->node[] array. Note that other CPUs - * will access only the leaves of the hierarchy, thus seeing that no - * grace period is in progress, at least until the corresponding - * leaf node has been initialized. In addition, we have excluded - * CPU-hotplug operations. - * - * The grace period cannot complete until the initialization - * process finishes, because this kthread handles both. - */ - rcu_for_each_node_breadth_first(rsp, rnp) { - raw_spin_lock_irq(&rnp->lock); - rdp = this_cpu_ptr(rsp->rda); - rcu_preempt_check_blocked_tasks(rnp); - rnp->qsmask = rnp->qsmaskinit; - ACCESS_ONCE(rnp->gpnum) = rsp->gpnum; - WARN_ON_ONCE(rnp->completed != rsp->completed); - ACCESS_ONCE(rnp->completed) = rsp->completed; - if (rnp == rdp->mynode) - __note_gp_changes(rsp, rnp, rdp); - rcu_preempt_boost_start_gp(rnp); - trace_rcu_grace_period_init(rsp->name, rnp->gpnum, - rnp->level, rnp->grplo, - rnp->grphi, rnp->qsmask); - raw_spin_unlock_irq(&rnp->lock); -#ifdef CONFIG_PROVE_RCU_DELAY - if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 && - system_state == SYSTEM_RUNNING) - udelay(200); -#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */ - cond_resched(); - } - - mutex_unlock(&rsp->onoff_mutex); - return 1; -} - -/* - * Do one round of quiescent-state forcing. - */ -int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) -{ - int fqs_state = fqs_state_in; - bool isidle = false; - unsigned long maxj; - struct rcu_node *rnp = rcu_get_root(rsp); - - rsp->n_force_qs++; - if (fqs_state == RCU_SAVE_DYNTICK) { - /* Collect dyntick-idle snapshots. */ - if (is_sysidle_rcu_state(rsp)) { - isidle = 1; - maxj = jiffies - ULONG_MAX / 4; - } - force_qs_rnp(rsp, dyntick_save_progress_counter, - &isidle, &maxj); - rcu_sysidle_report_gp(rsp, isidle, maxj); - fqs_state = RCU_FORCE_QS; - } else { - /* Handle dyntick-idle and offline CPUs. */ - isidle = 0; - force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj); - } - /* Clear flag to prevent immediate re-entry. */ - if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { - raw_spin_lock_irq(&rnp->lock); - rsp->gp_flags &= ~RCU_GP_FLAG_FQS; - raw_spin_unlock_irq(&rnp->lock); - } - return fqs_state; -} - -/* - * Clean up after the old grace period. - */ -static void rcu_gp_cleanup(struct rcu_state *rsp) -{ - unsigned long gp_duration; - int nocb = 0; - struct rcu_data *rdp; - struct rcu_node *rnp = rcu_get_root(rsp); - - raw_spin_lock_irq(&rnp->lock); - gp_duration = jiffies - rsp->gp_start; - if (gp_duration > rsp->gp_max) - rsp->gp_max = gp_duration; - - /* - * We know the grace period is complete, but to everyone else - * it appears to still be ongoing. But it is also the case - * that to everyone else it looks like there is nothing that - * they can do to advance the grace period. It is therefore - * safe for us to drop the lock in order to mark the grace - * period as completed in all of the rcu_node structures. - */ - raw_spin_unlock_irq(&rnp->lock); - - /* - * Propagate new ->completed value to rcu_node structures so - * that other CPUs don't have to wait until the start of the next - * grace period to process their callbacks. This also avoids - * some nasty RCU grace-period initialization races by forcing - * the end of the current grace period to be completely recorded in - * all of the rcu_node structures before the beginning of the next - * grace period is recorded in any of the rcu_node structures. - */ - rcu_for_each_node_breadth_first(rsp, rnp) { - raw_spin_lock_irq(&rnp->lock); - ACCESS_ONCE(rnp->completed) = rsp->gpnum; - rdp = this_cpu_ptr(rsp->rda); - if (rnp == rdp->mynode) - __note_gp_changes(rsp, rnp, rdp); - nocb += rcu_future_gp_cleanup(rsp, rnp); - raw_spin_unlock_irq(&rnp->lock); - cond_resched(); - } - rnp = rcu_get_root(rsp); - raw_spin_lock_irq(&rnp->lock); - rcu_nocb_gp_set(rnp, nocb); - - rsp->completed = rsp->gpnum; /* Declare grace period done. */ - trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end")); - rsp->fqs_state = RCU_GP_IDLE; - rdp = this_cpu_ptr(rsp->rda); - rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */ - if (cpu_needs_another_gp(rsp, rdp)) - rsp->gp_flags = 1; - raw_spin_unlock_irq(&rnp->lock); -} - -/* - * Body of kthread that handles grace periods. - */ -static int __noreturn rcu_gp_kthread(void *arg) -{ - int fqs_state; - unsigned long j; - int ret; - struct rcu_state *rsp = arg; - struct rcu_node *rnp = rcu_get_root(rsp); - - for (;;) { - - /* Handle grace-period start. */ - for (;;) { - wait_event_interruptible(rsp->gp_wq, - rsp->gp_flags & - RCU_GP_FLAG_INIT); - if ((rsp->gp_flags & RCU_GP_FLAG_INIT) && - rcu_gp_init(rsp)) - break; - cond_resched(); - flush_signals(current); - } - - /* Handle quiescent-state forcing. */ - fqs_state = RCU_SAVE_DYNTICK; - j = jiffies_till_first_fqs; - if (j > HZ) { - j = HZ; - jiffies_till_first_fqs = HZ; - } - for (;;) { - rsp->jiffies_force_qs = jiffies + j; - ret = wait_event_interruptible_timeout(rsp->gp_wq, - (rsp->gp_flags & RCU_GP_FLAG_FQS) || - (!ACCESS_ONCE(rnp->qsmask) && - !rcu_preempt_blocked_readers_cgp(rnp)), - j); - /* If grace period done, leave loop. */ - if (!ACCESS_ONCE(rnp->qsmask) && - !rcu_preempt_blocked_readers_cgp(rnp)) - break; - /* If time for quiescent-state forcing, do it. */ - if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) { - fqs_state = rcu_gp_fqs(rsp, fqs_state); - cond_resched(); - } else { - /* Deal with stray signal. */ - cond_resched(); - flush_signals(current); - } - j = jiffies_till_next_fqs; - if (j > HZ) { - j = HZ; - jiffies_till_next_fqs = HZ; - } else if (j < 1) { - j = 1; - jiffies_till_next_fqs = 1; - } - } - - /* Handle grace-period end. */ - rcu_gp_cleanup(rsp); - } -} - -static void rsp_wakeup(struct irq_work *work) -{ - struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work); - - /* Wake up rcu_gp_kthread() to start the grace period. */ - wake_up(&rsp->gp_wq); -} - -/* - * Start a new RCU grace period if warranted, re-initializing the hierarchy - * in preparation for detecting the next grace period. The caller must hold - * the root node's ->lock and hard irqs must be disabled. - * - * Note that it is legal for a dying CPU (which is marked as offline) to - * invoke this function. This can happen when the dying CPU reports its - * quiescent state. - */ -static void -rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp) -{ - if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { - /* - * Either we have not yet spawned the grace-period - * task, this CPU does not need another grace period, - * or a grace period is already in progress. - * Either way, don't start a new grace period. - */ - return; - } - rsp->gp_flags = RCU_GP_FLAG_INIT; - - /* - * We can't do wakeups while holding the rnp->lock, as that - * could cause possible deadlocks with the rq->lock. Defer - * the wakeup to interrupt context. And don't bother waking - * up the running kthread. - */ - if (current != rsp->gp_kthread) - irq_work_queue(&rsp->wakeup_work); -} - -/* - * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's - * callbacks. Note that rcu_start_gp_advanced() cannot do this because it - * is invoked indirectly from rcu_advance_cbs(), which would result in - * endless recursion -- or would do so if it wasn't for the self-deadlock - * that is encountered beforehand. - */ -static void -rcu_start_gp(struct rcu_state *rsp) -{ - struct rcu_data *rdp = this_cpu_ptr(rsp->rda); - struct rcu_node *rnp = rcu_get_root(rsp); - - /* - * If there is no grace period in progress right now, any - * callbacks we have up to this point will be satisfied by the - * next grace period. Also, advancing the callbacks reduces the - * probability of false positives from cpu_needs_another_gp() - * resulting in pointless grace periods. So, advance callbacks - * then start the grace period! - */ - rcu_advance_cbs(rsp, rnp, rdp); - rcu_start_gp_advanced(rsp, rnp, rdp); -} - -/* - * Report a full set of quiescent states to the specified rcu_state - * data structure. This involves cleaning up after the prior grace - * period and letting rcu_start_gp() start up the next grace period - * if one is needed. Note that the caller must hold rnp->lock, which - * is released before return. - */ -static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) - __releases(rcu_get_root(rsp)->lock) -{ - WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); - raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); - wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ -} - -/* - * Similar to rcu_report_qs_rdp(), for which it is a helper function. - * Allows quiescent states for a group of CPUs to be reported at one go - * to the specified rcu_node structure, though all the CPUs in the group - * must be represented by the same rcu_node structure (which need not be - * a leaf rcu_node structure, though it often will be). That structure's - * lock must be held upon entry, and it is released before return. - */ -static void -rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, - struct rcu_node *rnp, unsigned long flags) - __releases(rnp->lock) -{ - struct rcu_node *rnp_c; - - /* Walk up the rcu_node hierarchy. */ - for (;;) { - if (!(rnp->qsmask & mask)) { - - /* Our bit has already been cleared, so done. */ - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - rnp->qsmask &= ~mask; - trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, - mask, rnp->qsmask, rnp->level, - rnp->grplo, rnp->grphi, - !!rnp->gp_tasks); - if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { - - /* Other bits still set at this level, so done. */ - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - mask = rnp->grpmask; - if (rnp->parent == NULL) { - - /* No more levels. Exit loop holding root lock. */ - - break; - } - raw_spin_unlock_irqrestore(&rnp->lock, flags); - rnp_c = rnp; - rnp = rnp->parent; - raw_spin_lock_irqsave(&rnp->lock, flags); - WARN_ON_ONCE(rnp_c->qsmask); - } - - /* - * Get here if we are the last CPU to pass through a quiescent - * state for this grace period. Invoke rcu_report_qs_rsp() - * to clean up and start the next grace period if one is needed. - */ - rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ -} - -/* - * Record a quiescent state for the specified CPU to that CPU's rcu_data - * structure. This must be either called from the specified CPU, or - * called when the specified CPU is known to be offline (and when it is - * also known that no other CPU is concurrently trying to help the offline - * CPU). The lastcomp argument is used to make sure we are still in the - * grace period of interest. We don't want to end the current grace period - * based on quiescent states detected in an earlier grace period! - */ -static void -rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - unsigned long mask; - struct rcu_node *rnp; - - rnp = rdp->mynode; - raw_spin_lock_irqsave(&rnp->lock, flags); - if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum || - rnp->completed == rnp->gpnum) { - - /* - * The grace period in which this quiescent state was - * recorded has ended, so don't report it upwards. - * We will instead need a new quiescent state that lies - * within the current grace period. - */ - rdp->passed_quiesce = 0; /* need qs for new gp. */ - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - mask = rdp->grpmask; - if ((rnp->qsmask & mask) == 0) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } else { - rdp->qs_pending = 0; - - /* - * This GP can't end until cpu checks in, so all of our - * callbacks can be processed during the next GP. - */ - rcu_accelerate_cbs(rsp, rnp, rdp); - - rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ - } -} - -/* - * Check to see if there is a new grace period of which this CPU - * is not yet aware, and if so, set up local rcu_data state for it. - * Otherwise, see if this CPU has just passed through its first - * quiescent state for this grace period, and record that fact if so. - */ -static void -rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) -{ - /* Check for grace-period ends and beginnings. */ - note_gp_changes(rsp, rdp); - - /* - * Does this CPU still need to do its part for current grace period? - * If no, return and let the other CPUs do their part as well. - */ - if (!rdp->qs_pending) - return; - - /* - * Was there a quiescent state since the beginning of the grace - * period? If no, then exit and wait for the next call. - */ - if (!rdp->passed_quiesce) - return; - - /* - * Tell RCU we are done (but rcu_report_qs_rdp() will be the - * judge of that). - */ - rcu_report_qs_rdp(rdp->cpu, rsp, rdp); -} - -#ifdef CONFIG_HOTPLUG_CPU - -/* - * Send the specified CPU's RCU callbacks to the orphanage. The - * specified CPU must be offline, and the caller must hold the - * ->orphan_lock. - */ -static void -rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, - struct rcu_node *rnp, struct rcu_data *rdp) -{ - /* No-CBs CPUs do not have orphanable callbacks. */ - if (rcu_is_nocb_cpu(rdp->cpu)) - return; - - /* - * Orphan the callbacks. First adjust the counts. This is safe - * because _rcu_barrier() excludes CPU-hotplug operations, so it - * cannot be running now. Thus no memory barrier is required. - */ - if (rdp->nxtlist != NULL) { - rsp->qlen_lazy += rdp->qlen_lazy; - rsp->qlen += rdp->qlen; - rdp->n_cbs_orphaned += rdp->qlen; - rdp->qlen_lazy = 0; - ACCESS_ONCE(rdp->qlen) = 0; - } - - /* - * Next, move those callbacks still needing a grace period to - * the orphanage, where some other CPU will pick them up. - * Some of the callbacks might have gone partway through a grace - * period, but that is too bad. They get to start over because we - * cannot assume that grace periods are synchronized across CPUs. - * We don't bother updating the ->nxttail[] array yet, instead - * we just reset the whole thing later on. - */ - if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { - *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; - rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; - *rdp->nxttail[RCU_DONE_TAIL] = NULL; - } - - /* - * Then move the ready-to-invoke callbacks to the orphanage, - * where some other CPU will pick them up. These will not be - * required to pass though another grace period: They are done. - */ - if (rdp->nxtlist != NULL) { - *rsp->orphan_donetail = rdp->nxtlist; - rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; - } - - /* Finally, initialize the rcu_data structure's list to empty. */ - init_callback_list(rdp); -} - -/* - * Adopt the RCU callbacks from the specified rcu_state structure's - * orphanage. The caller must hold the ->orphan_lock. - */ -static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) -{ - int i; - struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); - - /* No-CBs CPUs are handled specially. */ - if (rcu_nocb_adopt_orphan_cbs(rsp, rdp)) - return; - - /* Do the accounting first. */ - rdp->qlen_lazy += rsp->qlen_lazy; - rdp->qlen += rsp->qlen; - rdp->n_cbs_adopted += rsp->qlen; - if (rsp->qlen_lazy != rsp->qlen) - rcu_idle_count_callbacks_posted(); - rsp->qlen_lazy = 0; - rsp->qlen = 0; - - /* - * We do not need a memory barrier here because the only way we - * can get here if there is an rcu_barrier() in flight is if - * we are the task doing the rcu_barrier(). - */ - - /* First adopt the ready-to-invoke callbacks. */ - if (rsp->orphan_donelist != NULL) { - *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; - *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; - for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) - if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) - rdp->nxttail[i] = rsp->orphan_donetail; - rsp->orphan_donelist = NULL; - rsp->orphan_donetail = &rsp->orphan_donelist; - } - - /* And then adopt the callbacks that still need a grace period. */ - if (rsp->orphan_nxtlist != NULL) { - *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; - rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; - rsp->orphan_nxtlist = NULL; - rsp->orphan_nxttail = &rsp->orphan_nxtlist; - } -} - -/* - * Trace the fact that this CPU is going offline. - */ -static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) -{ - RCU_TRACE(unsigned long mask); - RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); - RCU_TRACE(struct rcu_node *rnp = rdp->mynode); - - RCU_TRACE(mask = rdp->grpmask); - trace_rcu_grace_period(rsp->name, - rnp->gpnum + 1 - !!(rnp->qsmask & mask), - TPS("cpuofl")); -} - -/* - * The CPU has been completely removed, and some other CPU is reporting - * this fact from process context. Do the remainder of the cleanup, - * including orphaning the outgoing CPU's RCU callbacks, and also - * adopting them. There can only be one CPU hotplug operation at a time, - * so no other CPU can be attempting to update rcu_cpu_kthread_task. - */ -static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) -{ - unsigned long flags; - unsigned long mask; - int need_report = 0; - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ - - /* Adjust any no-longer-needed kthreads. */ - rcu_boost_kthread_setaffinity(rnp, -1); - - /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ - - /* Exclude any attempts to start a new grace period. */ - mutex_lock(&rsp->onoff_mutex); - raw_spin_lock_irqsave(&rsp->orphan_lock, flags); - - /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ - rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); - rcu_adopt_orphan_cbs(rsp); - - /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ - mask = rdp->grpmask; /* rnp->grplo is constant. */ - do { - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rnp->qsmaskinit &= ~mask; - if (rnp->qsmaskinit != 0) { - if (rnp != rdp->mynode) - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - break; - } - if (rnp == rdp->mynode) - need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); - else - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - mask = rnp->grpmask; - rnp = rnp->parent; - } while (rnp != NULL); - - /* - * We still hold the leaf rcu_node structure lock here, and - * irqs are still disabled. The reason for this subterfuge is - * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock - * held leads to deadlock. - */ - raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */ - rnp = rdp->mynode; - if (need_report & RCU_OFL_TASKS_NORM_GP) - rcu_report_unblock_qs_rnp(rnp, flags); - else - raw_spin_unlock_irqrestore(&rnp->lock, flags); - if (need_report & RCU_OFL_TASKS_EXP_GP) - rcu_report_exp_rnp(rsp, rnp, true); - WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, - "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", - cpu, rdp->qlen, rdp->nxtlist); - init_callback_list(rdp); - /* Disallow further callbacks on this CPU. */ - rdp->nxttail[RCU_NEXT_TAIL] = NULL; - mutex_unlock(&rsp->onoff_mutex); -} - -#else /* #ifdef CONFIG_HOTPLUG_CPU */ - -static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) -{ -} - -static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) -{ -} - -#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ - -/* - * Invoke any RCU callbacks that have made it to the end of their grace - * period. Thottle as specified by rdp->blimit. - */ -static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) -{ - unsigned long flags; - struct rcu_head *next, *list, **tail; - long bl, count, count_lazy; - int i; - - /* If no callbacks are ready, just return. */ - if (!cpu_has_callbacks_ready_to_invoke(rdp)) { - trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); - trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), - need_resched(), is_idle_task(current), - rcu_is_callbacks_kthread()); - return; - } - - /* - * Extract the list of ready callbacks, disabling to prevent - * races with call_rcu() from interrupt handlers. - */ - local_irq_save(flags); - WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); - bl = rdp->blimit; - trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); - list = rdp->nxtlist; - rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; - *rdp->nxttail[RCU_DONE_TAIL] = NULL; - tail = rdp->nxttail[RCU_DONE_TAIL]; - for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) - if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) - rdp->nxttail[i] = &rdp->nxtlist; - local_irq_restore(flags); - - /* Invoke callbacks. */ - count = count_lazy = 0; - while (list) { - next = list->next; - prefetch(next); - debug_rcu_head_unqueue(list); - if (__rcu_reclaim(rsp->name, list)) - count_lazy++; - list = next; - /* Stop only if limit reached and CPU has something to do. */ - if (++count >= bl && - (need_resched() || - (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) - break; - } - - local_irq_save(flags); - trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), - is_idle_task(current), - rcu_is_callbacks_kthread()); - - /* Update count, and requeue any remaining callbacks. */ - if (list != NULL) { - *tail = rdp->nxtlist; - rdp->nxtlist = list; - for (i = 0; i < RCU_NEXT_SIZE; i++) - if (&rdp->nxtlist == rdp->nxttail[i]) - rdp->nxttail[i] = tail; - else - break; - } - smp_mb(); /* List handling before counting for rcu_barrier(). */ - rdp->qlen_lazy -= count_lazy; - ACCESS_ONCE(rdp->qlen) -= count; - rdp->n_cbs_invoked += count; - - /* Reinstate batch limit if we have worked down the excess. */ - if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) - rdp->blimit = blimit; - - /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ - if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { - rdp->qlen_last_fqs_check = 0; - rdp->n_force_qs_snap = rsp->n_force_qs; - } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) - rdp->qlen_last_fqs_check = rdp->qlen; - WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); - - local_irq_restore(flags); - - /* Re-invoke RCU core processing if there are callbacks remaining. */ - if (cpu_has_callbacks_ready_to_invoke(rdp)) - invoke_rcu_core(); -} - -/* - * Check to see if this CPU is in a non-context-switch quiescent state - * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). - * Also schedule RCU core processing. - * - * This function must be called from hardirq context. It is normally - * invoked from the scheduling-clock interrupt. If rcu_pending returns - * false, there is no point in invoking rcu_check_callbacks(). - */ -void rcu_check_callbacks(int cpu, int user) -{ - trace_rcu_utilization(TPS("Start scheduler-tick")); - increment_cpu_stall_ticks(); - if (user || rcu_is_cpu_rrupt_from_idle()) { - - /* - * Get here if this CPU took its interrupt from user - * mode or from the idle loop, and if this is not a - * nested interrupt. In this case, the CPU is in - * a quiescent state, so note it. - * - * No memory barrier is required here because both - * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local - * variables that other CPUs neither access nor modify, - * at least not while the corresponding CPU is online. - */ - - rcu_sched_qs(cpu); - rcu_bh_qs(cpu); - - } else if (!in_softirq()) { - - /* - * Get here if this CPU did not take its interrupt from - * softirq, in other words, if it is not interrupting - * a rcu_bh read-side critical section. This is an _bh - * critical section, so note it. - */ - - rcu_bh_qs(cpu); - } - rcu_preempt_check_callbacks(cpu); - if (rcu_pending(cpu)) - invoke_rcu_core(); - trace_rcu_utilization(TPS("End scheduler-tick")); -} - -/* - * Scan the leaf rcu_node structures, processing dyntick state for any that - * have not yet encountered a quiescent state, using the function specified. - * Also initiate boosting for any threads blocked on the root rcu_node. - * - * The caller must have suppressed start of new grace periods. - */ -static void force_qs_rnp(struct rcu_state *rsp, - int (*f)(struct rcu_data *rsp, bool *isidle, - unsigned long *maxj), - bool *isidle, unsigned long *maxj) -{ - unsigned long bit; - int cpu; - unsigned long flags; - unsigned long mask; - struct rcu_node *rnp; - - rcu_for_each_leaf_node(rsp, rnp) { - cond_resched(); - mask = 0; - raw_spin_lock_irqsave(&rnp->lock, flags); - if (!rcu_gp_in_progress(rsp)) { - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - if (rnp->qsmask == 0) { - rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ - continue; - } - cpu = rnp->grplo; - bit = 1; - for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { - if ((rnp->qsmask & bit) != 0) { - if ((rnp->qsmaskinit & bit) != 0) - *isidle = 0; - if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) - mask |= bit; - } - } - if (mask != 0) { - - /* rcu_report_qs_rnp() releases rnp->lock. */ - rcu_report_qs_rnp(mask, rsp, rnp, flags); - continue; - } - raw_spin_unlock_irqrestore(&rnp->lock, flags); - } - rnp = rcu_get_root(rsp); - if (rnp->qsmask == 0) { - raw_spin_lock_irqsave(&rnp->lock, flags); - rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ - } -} - -/* - * Force quiescent states on reluctant CPUs, and also detect which - * CPUs are in dyntick-idle mode. - */ -static void force_quiescent_state(struct rcu_state *rsp) -{ - unsigned long flags; - bool ret; - struct rcu_node *rnp; - struct rcu_node *rnp_old = NULL; - - /* Funnel through hierarchy to reduce memory contention. */ - rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode; - for (; rnp != NULL; rnp = rnp->parent) { - ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || - !raw_spin_trylock(&rnp->fqslock); - if (rnp_old != NULL) - raw_spin_unlock(&rnp_old->fqslock); - if (ret) { - rsp->n_force_qs_lh++; - return; - } - rnp_old = rnp; - } - /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ - - /* Reached the root of the rcu_node tree, acquire lock. */ - raw_spin_lock_irqsave(&rnp_old->lock, flags); - raw_spin_unlock(&rnp_old->fqslock); - if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { - rsp->n_force_qs_lh++; - raw_spin_unlock_irqrestore(&rnp_old->lock, flags); - return; /* Someone beat us to it. */ - } - rsp->gp_flags |= RCU_GP_FLAG_FQS; - raw_spin_unlock_irqrestore(&rnp_old->lock, flags); - wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ -} - -/* - * This does the RCU core processing work for the specified rcu_state - * and rcu_data structures. This may be called only from the CPU to - * whom the rdp belongs. - */ -static void -__rcu_process_callbacks(struct rcu_state *rsp) -{ - unsigned long flags; - struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); - - WARN_ON_ONCE(rdp->beenonline == 0); - - /* Update RCU state based on any recent quiescent states. */ - rcu_check_quiescent_state(rsp, rdp); - - /* Does this CPU require a not-yet-started grace period? */ - local_irq_save(flags); - if (cpu_needs_another_gp(rsp, rdp)) { - raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */ - rcu_start_gp(rsp); - raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); - } else { - local_irq_restore(flags); - } - - /* If there are callbacks ready, invoke them. */ - if (cpu_has_callbacks_ready_to_invoke(rdp)) - invoke_rcu_callbacks(rsp, rdp); -} - -/* - * Do RCU core processing for the current CPU. - */ -static void rcu_process_callbacks(struct softirq_action *unused) -{ - struct rcu_state *rsp; - - if (cpu_is_offline(smp_processor_id())) - return; - trace_rcu_utilization(TPS("Start RCU core")); - for_each_rcu_flavor(rsp) - __rcu_process_callbacks(rsp); - trace_rcu_utilization(TPS("End RCU core")); -} - -/* - * Schedule RCU callback invocation. If the specified type of RCU - * does not support RCU priority boosting, just do a direct call, - * otherwise wake up the per-CPU kernel kthread. Note that because we - * are running on the current CPU with interrupts disabled, the - * rcu_cpu_kthread_task cannot disappear out from under us. - */ -static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) -{ - if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) - return; - if (likely(!rsp->boost)) { - rcu_do_batch(rsp, rdp); - return; - } - invoke_rcu_callbacks_kthread(); -} - -static void invoke_rcu_core(void) -{ - if (cpu_online(smp_processor_id())) - raise_softirq(RCU_SOFTIRQ); -} - -/* - * Handle any core-RCU processing required by a call_rcu() invocation. - */ -static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, - struct rcu_head *head, unsigned long flags) -{ - /* - * If called from an extended quiescent state, invoke the RCU - * core in order to force a re-evaluation of RCU's idleness. - */ - if (rcu_is_cpu_idle() && cpu_online(smp_processor_id())) - invoke_rcu_core(); - - /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ - if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) - return; - - /* - * Force the grace period if too many callbacks or too long waiting. - * Enforce hysteresis, and don't invoke force_quiescent_state() - * if some other CPU has recently done so. Also, don't bother - * invoking force_quiescent_state() if the newly enqueued callback - * is the only one waiting for a grace period to complete. - */ - if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { - - /* Are we ignoring a completed grace period? */ - note_gp_changes(rsp, rdp); - - /* Start a new grace period if one not already started. */ - if (!rcu_gp_in_progress(rsp)) { - struct rcu_node *rnp_root = rcu_get_root(rsp); - - raw_spin_lock(&rnp_root->lock); - rcu_start_gp(rsp); - raw_spin_unlock(&rnp_root->lock); - } else { - /* Give the grace period a kick. */ - rdp->blimit = LONG_MAX; - if (rsp->n_force_qs == rdp->n_force_qs_snap && - *rdp->nxttail[RCU_DONE_TAIL] != head) - force_quiescent_state(rsp); - rdp->n_force_qs_snap = rsp->n_force_qs; - rdp->qlen_last_fqs_check = rdp->qlen; - } - } -} - -/* - * RCU callback function to leak a callback. - */ -static void rcu_leak_callback(struct rcu_head *rhp) -{ -} - -/* - * Helper function for call_rcu() and friends. The cpu argument will - * normally be -1, indicating "currently running CPU". It may specify - * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() - * is expected to specify a CPU. - */ -static void -__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), - struct rcu_state *rsp, int cpu, bool lazy) -{ - unsigned long flags; - struct rcu_data *rdp; - - WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ - if (debug_rcu_head_queue(head)) { - /* Probable double call_rcu(), so leak the callback. */ - ACCESS_ONCE(head->func) = rcu_leak_callback; - WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n"); - return; - } - head->func = func; - head->next = NULL; - - /* - * Opportunistically note grace-period endings and beginnings. - * Note that we might see a beginning right after we see an - * end, but never vice versa, since this CPU has to pass through - * a quiescent state betweentimes. - */ - local_irq_save(flags); - rdp = this_cpu_ptr(rsp->rda); - - /* Add the callback to our list. */ - if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) { - int offline; - - if (cpu != -1) - rdp = per_cpu_ptr(rsp->rda, cpu); - offline = !__call_rcu_nocb(rdp, head, lazy); - WARN_ON_ONCE(offline); - /* _call_rcu() is illegal on offline CPU; leak the callback. */ - local_irq_restore(flags); - return; - } - ACCESS_ONCE(rdp->qlen)++; - if (lazy) - rdp->qlen_lazy++; - else - rcu_idle_count_callbacks_posted(); - smp_mb(); /* Count before adding callback for rcu_barrier(). */ - *rdp->nxttail[RCU_NEXT_TAIL] = head; - rdp->nxttail[RCU_NEXT_TAIL] = &head->next; - - if (__is_kfree_rcu_offset((unsigned long)func)) - trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, - rdp->qlen_lazy, rdp->qlen); - else - trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); - - /* Go handle any RCU core processing required. */ - __call_rcu_core(rsp, rdp, head, flags); - local_irq_restore(flags); -} - -/* - * Queue an RCU-sched callback for invocation after a grace period. - */ -void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - __call_rcu(head, func, &rcu_sched_state, -1, 0); -} -EXPORT_SYMBOL_GPL(call_rcu_sched); - -/* - * Queue an RCU callback for invocation after a quicker grace period. - */ -void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - __call_rcu(head, func, &rcu_bh_state, -1, 0); -} -EXPORT_SYMBOL_GPL(call_rcu_bh); - -/* - * Because a context switch is a grace period for RCU-sched and RCU-bh, - * any blocking grace-period wait automatically implies a grace period - * if there is only one CPU online at any point time during execution - * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to - * occasionally incorrectly indicate that there are multiple CPUs online - * when there was in fact only one the whole time, as this just adds - * some overhead: RCU still operates correctly. - */ -static inline int rcu_blocking_is_gp(void) -{ - int ret; - - might_sleep(); /* Check for RCU read-side critical section. */ - preempt_disable(); - ret = num_online_cpus() <= 1; - preempt_enable(); - return ret; -} - -/** - * synchronize_sched - wait until an rcu-sched grace period has elapsed. - * - * Control will return to the caller some time after a full rcu-sched - * grace period has elapsed, in other words after all currently executing - * rcu-sched read-side critical sections have completed. These read-side - * critical sections are delimited by rcu_read_lock_sched() and - * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), - * local_irq_disable(), and so on may be used in place of - * rcu_read_lock_sched(). - * - * This means that all preempt_disable code sequences, including NMI and - * non-threaded hardware-interrupt handlers, in progress on entry will - * have completed before this primitive returns. However, this does not - * guarantee that softirq handlers will have completed, since in some - * kernels, these handlers can run in process context, and can block. - * - * Note that this guarantee implies further memory-ordering guarantees. - * On systems with more than one CPU, when synchronize_sched() returns, - * each CPU is guaranteed to have executed a full memory barrier since the - * end of its last RCU-sched read-side critical section whose beginning - * preceded the call to synchronize_sched(). In addition, each CPU having - * an RCU read-side critical section that extends beyond the return from - * synchronize_sched() is guaranteed to have executed a full memory barrier - * after the beginning of synchronize_sched() and before the beginning of - * that RCU read-side critical section. Note that these guarantees include - * CPUs that are offline, idle, or executing in user mode, as well as CPUs - * that are executing in the kernel. - * - * Furthermore, if CPU A invoked synchronize_sched(), which returned - * to its caller on CPU B, then both CPU A and CPU B are guaranteed - * to have executed a full memory barrier during the execution of - * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but - * again only if the system has more than one CPU). - * - * This primitive provides the guarantees made by the (now removed) - * synchronize_kernel() API. In contrast, synchronize_rcu() only - * guarantees that rcu_read_lock() sections will have completed. - * In "classic RCU", these two guarantees happen to be one and - * the same, but can differ in realtime RCU implementations. - */ -void synchronize_sched(void) -{ - rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && - !lock_is_held(&rcu_lock_map) && - !lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_sched() in RCU-sched read-side critical section"); - if (rcu_blocking_is_gp()) - return; - if (rcu_expedited) - synchronize_sched_expedited(); - else - wait_rcu_gp(call_rcu_sched); -} -EXPORT_SYMBOL_GPL(synchronize_sched); - -/** - * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. - * - * Control will return to the caller some time after a full rcu_bh grace - * period has elapsed, in other words after all currently executing rcu_bh - * read-side critical sections have completed. RCU read-side critical - * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), - * and may be nested. - * - * See the description of synchronize_sched() for more detailed information - * on memory ordering guarantees. - */ -void synchronize_rcu_bh(void) -{ - rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && - !lock_is_held(&rcu_lock_map) && - !lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); - if (rcu_blocking_is_gp()) - return; - if (rcu_expedited) - synchronize_rcu_bh_expedited(); - else - wait_rcu_gp(call_rcu_bh); -} -EXPORT_SYMBOL_GPL(synchronize_rcu_bh); - -static int synchronize_sched_expedited_cpu_stop(void *data) -{ - /* - * There must be a full memory barrier on each affected CPU - * between the time that try_stop_cpus() is called and the - * time that it returns. - * - * In the current initial implementation of cpu_stop, the - * above condition is already met when the control reaches - * this point and the following smp_mb() is not strictly - * necessary. Do smp_mb() anyway for documentation and - * robustness against future implementation changes. - */ - smp_mb(); /* See above comment block. */ - return 0; -} - -/** - * synchronize_sched_expedited - Brute-force RCU-sched grace period - * - * Wait for an RCU-sched grace period to elapse, but use a "big hammer" - * approach to force the grace period to end quickly. This consumes - * significant time on all CPUs and is unfriendly to real-time workloads, - * so is thus not recommended for any sort of common-case code. In fact, - * if you are using synchronize_sched_expedited() in a loop, please - * restructure your code to batch your updates, and then use a single - * synchronize_sched() instead. - * - * Note that it is illegal to call this function while holding any lock - * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal - * to call this function from a CPU-hotplug notifier. Failing to observe - * these restriction will result in deadlock. - * - * This implementation can be thought of as an application of ticket - * locking to RCU, with sync_sched_expedited_started and - * sync_sched_expedited_done taking on the roles of the halves - * of the ticket-lock word. Each task atomically increments - * sync_sched_expedited_started upon entry, snapshotting the old value, - * then attempts to stop all the CPUs. If this succeeds, then each - * CPU will have executed a context switch, resulting in an RCU-sched - * grace period. We are then done, so we use atomic_cmpxchg() to - * update sync_sched_expedited_done to match our snapshot -- but - * only if someone else has not already advanced past our snapshot. - * - * On the other hand, if try_stop_cpus() fails, we check the value - * of sync_sched_expedited_done. If it has advanced past our - * initial snapshot, then someone else must have forced a grace period - * some time after we took our snapshot. In this case, our work is - * done for us, and we can simply return. Otherwise, we try again, - * but keep our initial snapshot for purposes of checking for someone - * doing our work for us. - * - * If we fail too many times in a row, we fall back to synchronize_sched(). - */ -void synchronize_sched_expedited(void) -{ - long firstsnap, s, snap; - int trycount = 0; - struct rcu_state *rsp = &rcu_sched_state; - - /* - * If we are in danger of counter wrap, just do synchronize_sched(). - * By allowing sync_sched_expedited_started to advance no more than - * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring - * that more than 3.5 billion CPUs would be required to force a - * counter wrap on a 32-bit system. Quite a few more CPUs would of - * course be required on a 64-bit system. - */ - if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start), - (ulong)atomic_long_read(&rsp->expedited_done) + - ULONG_MAX / 8)) { - synchronize_sched(); - atomic_long_inc(&rsp->expedited_wrap); - return; - } - - /* - * Take a ticket. Note that atomic_inc_return() implies a - * full memory barrier. - */ - snap = atomic_long_inc_return(&rsp->expedited_start); - firstsnap = snap; - get_online_cpus(); - WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); - - /* - * Each pass through the following loop attempts to force a - * context switch on each CPU. - */ - while (try_stop_cpus(cpu_online_mask, - synchronize_sched_expedited_cpu_stop, - NULL) == -EAGAIN) { - put_online_cpus(); - atomic_long_inc(&rsp->expedited_tryfail); - - /* Check to see if someone else did our work for us. */ - s = atomic_long_read(&rsp->expedited_done); - if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { - /* ensure test happens before caller kfree */ - smp_mb__before_atomic_inc(); /* ^^^ */ - atomic_long_inc(&rsp->expedited_workdone1); - return; - } - - /* No joy, try again later. Or just synchronize_sched(). */ - if (trycount++ < 10) { - udelay(trycount * num_online_cpus()); - } else { - wait_rcu_gp(call_rcu_sched); - atomic_long_inc(&rsp->expedited_normal); - return; - } - - /* Recheck to see if someone else did our work for us. */ - s = atomic_long_read(&rsp->expedited_done); - if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { - /* ensure test happens before caller kfree */ - smp_mb__before_atomic_inc(); /* ^^^ */ - atomic_long_inc(&rsp->expedited_workdone2); - return; - } - - /* - * Refetching sync_sched_expedited_started allows later - * callers to piggyback on our grace period. We retry - * after they started, so our grace period works for them, - * and they started after our first try, so their grace - * period works for us. - */ - get_online_cpus(); - snap = atomic_long_read(&rsp->expedited_start); - smp_mb(); /* ensure read is before try_stop_cpus(). */ - } - atomic_long_inc(&rsp->expedited_stoppedcpus); - - /* - * Everyone up to our most recent fetch is covered by our grace - * period. Update the counter, but only if our work is still - * relevant -- which it won't be if someone who started later - * than we did already did their update. - */ - do { - atomic_long_inc(&rsp->expedited_done_tries); - s = atomic_long_read(&rsp->expedited_done); - if (ULONG_CMP_GE((ulong)s, (ulong)snap)) { - /* ensure test happens before caller kfree */ - smp_mb__before_atomic_inc(); /* ^^^ */ - atomic_long_inc(&rsp->expedited_done_lost); - break; - } - } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s); - atomic_long_inc(&rsp->expedited_done_exit); - - put_online_cpus(); -} -EXPORT_SYMBOL_GPL(synchronize_sched_expedited); - -/* - * Check to see if there is any immediate RCU-related work to be done - * by the current CPU, for the specified type of RCU, returning 1 if so. - * The checks are in order of increasing expense: checks that can be - * carried out against CPU-local state are performed first. However, - * we must check for CPU stalls first, else we might not get a chance. - */ -static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) -{ - struct rcu_node *rnp = rdp->mynode; - - rdp->n_rcu_pending++; - - /* Check for CPU stalls, if enabled. */ - check_cpu_stall(rsp, rdp); - - /* Is the RCU core waiting for a quiescent state from this CPU? */ - if (rcu_scheduler_fully_active && - rdp->qs_pending && !rdp->passed_quiesce) { - rdp->n_rp_qs_pending++; - } else if (rdp->qs_pending && rdp->passed_quiesce) { - rdp->n_rp_report_qs++; - return 1; - } - - /* Does this CPU have callbacks ready to invoke? */ - if (cpu_has_callbacks_ready_to_invoke(rdp)) { - rdp->n_rp_cb_ready++; - return 1; - } - - /* Has RCU gone idle with this CPU needing another grace period? */ - if (cpu_needs_another_gp(rsp, rdp)) { - rdp->n_rp_cpu_needs_gp++; - return 1; - } - - /* Has another RCU grace period completed? */ - if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ - rdp->n_rp_gp_completed++; - return 1; - } - - /* Has a new RCU grace period started? */ - if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ - rdp->n_rp_gp_started++; - return 1; - } - - /* nothing to do */ - rdp->n_rp_need_nothing++; - return 0; -} - -/* - * Check to see if there is any immediate RCU-related work to be done - * by the current CPU, returning 1 if so. This function is part of the - * RCU implementation; it is -not- an exported member of the RCU API. - */ -static int rcu_pending(int cpu) -{ - struct rcu_state *rsp; - - for_each_rcu_flavor(rsp) - if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu))) - return 1; - return 0; -} - -/* - * Return true if the specified CPU has any callback. If all_lazy is - * non-NULL, store an indication of whether all callbacks are lazy. - * (If there are no callbacks, all of them are deemed to be lazy.) - */ -static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy) -{ - bool al = true; - bool hc = false; - struct rcu_data *rdp; - struct rcu_state *rsp; - - for_each_rcu_flavor(rsp) { - rdp = per_cpu_ptr(rsp->rda, cpu); - if (rdp->qlen != rdp->qlen_lazy) - al = false; - if (rdp->nxtlist) - hc = true; - } - if (all_lazy) - *all_lazy = al; - return hc; -} - -/* - * Helper function for _rcu_barrier() tracing. If tracing is disabled, - * the compiler is expected to optimize this away. - */ -static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s, - int cpu, unsigned long done) -{ - trace_rcu_barrier(rsp->name, s, cpu, - atomic_read(&rsp->barrier_cpu_count), done); -} - -/* - * RCU callback function for _rcu_barrier(). If we are last, wake - * up the task executing _rcu_barrier(). - */ -static void rcu_barrier_callback(struct rcu_head *rhp) -{ - struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); - struct rcu_state *rsp = rdp->rsp; - - if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { - _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); - complete(&rsp->barrier_completion); - } else { - _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); - } -} - -/* - * Called with preemption disabled, and from cross-cpu IRQ context. - */ -static void rcu_barrier_func(void *type) -{ - struct rcu_state *rsp = type; - struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); - - _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); - atomic_inc(&rsp->barrier_cpu_count); - rsp->call(&rdp->barrier_head, rcu_barrier_callback); -} - -/* - * Orchestrate the specified type of RCU barrier, waiting for all - * RCU callbacks of the specified type to complete. - */ -static void _rcu_barrier(struct rcu_state *rsp) -{ - int cpu; - struct rcu_data *rdp; - unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done); - unsigned long snap_done; - - _rcu_barrier_trace(rsp, "Begin", -1, snap); - - /* Take mutex to serialize concurrent rcu_barrier() requests. */ - mutex_lock(&rsp->barrier_mutex); - - /* - * Ensure that all prior references, including to ->n_barrier_done, - * are ordered before the _rcu_barrier() machinery. - */ - smp_mb(); /* See above block comment. */ - - /* - * Recheck ->n_barrier_done to see if others did our work for us. - * This means checking ->n_barrier_done for an even-to-odd-to-even - * transition. The "if" expression below therefore rounds the old - * value up to the next even number and adds two before comparing. - */ - snap_done = rsp->n_barrier_done; - _rcu_barrier_trace(rsp, "Check", -1, snap_done); - - /* - * If the value in snap is odd, we needed to wait for the current - * rcu_barrier() to complete, then wait for the next one, in other - * words, we need the value of snap_done to be three larger than - * the value of snap. On the other hand, if the value in snap is - * even, we only had to wait for the next rcu_barrier() to complete, - * in other words, we need the value of snap_done to be only two - * greater than the value of snap. The "(snap + 3) & ~0x1" computes - * this for us (thank you, Linus!). - */ - if (ULONG_CMP_GE(snap_done, (snap + 3) & ~0x1)) { - _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); - smp_mb(); /* caller's subsequent code after above check. */ - mutex_unlock(&rsp->barrier_mutex); - return; - } - - /* - * Increment ->n_barrier_done to avoid duplicate work. Use - * ACCESS_ONCE() to prevent the compiler from speculating - * the increment to precede the early-exit check. - */ - ACCESS_ONCE(rsp->n_barrier_done)++; - WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); - _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); - smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ - - /* - * Initialize the count to one rather than to zero in order to - * avoid a too-soon return to zero in case of a short grace period - * (or preemption of this task). Exclude CPU-hotplug operations - * to ensure that no offline CPU has callbacks queued. - */ - init_completion(&rsp->barrier_completion); - atomic_set(&rsp->barrier_cpu_count, 1); - get_online_cpus(); - - /* - * Force each CPU with callbacks to register a new callback. - * When that callback is invoked, we will know that all of the - * corresponding CPU's preceding callbacks have been invoked. - */ - for_each_possible_cpu(cpu) { - if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) - continue; - rdp = per_cpu_ptr(rsp->rda, cpu); - if (rcu_is_nocb_cpu(cpu)) { - _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, - rsp->n_barrier_done); - atomic_inc(&rsp->barrier_cpu_count); - __call_rcu(&rdp->barrier_head, rcu_barrier_callback, - rsp, cpu, 0); - } else if (ACCESS_ONCE(rdp->qlen)) { - _rcu_barrier_trace(rsp, "OnlineQ", cpu, - rsp->n_barrier_done); - smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); - } else { - _rcu_barrier_trace(rsp, "OnlineNQ", cpu, - rsp->n_barrier_done); - } - } - put_online_cpus(); - - /* - * Now that we have an rcu_barrier_callback() callback on each - * CPU, and thus each counted, remove the initial count. - */ - if (atomic_dec_and_test(&rsp->barrier_cpu_count)) - complete(&rsp->barrier_completion); - - /* Increment ->n_barrier_done to prevent duplicate work. */ - smp_mb(); /* Keep increment after above mechanism. */ - ACCESS_ONCE(rsp->n_barrier_done)++; - WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); - _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); - smp_mb(); /* Keep increment before caller's subsequent code. */ - - /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ - wait_for_completion(&rsp->barrier_completion); - - /* Other rcu_barrier() invocations can now safely proceed. */ - mutex_unlock(&rsp->barrier_mutex); -} - -/** - * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. - */ -void rcu_barrier_bh(void) -{ - _rcu_barrier(&rcu_bh_state); -} -EXPORT_SYMBOL_GPL(rcu_barrier_bh); - -/** - * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. - */ -void rcu_barrier_sched(void) -{ - _rcu_barrier(&rcu_sched_state); -} -EXPORT_SYMBOL_GPL(rcu_barrier_sched); - -/* - * Do boot-time initialization of a CPU's per-CPU RCU data. - */ -static void __init -rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) -{ - unsigned long flags; - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_node *rnp = rcu_get_root(rsp); - - /* Set up local state, ensuring consistent view of global state. */ - raw_spin_lock_irqsave(&rnp->lock, flags); - rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); - init_callback_list(rdp); - rdp->qlen_lazy = 0; - ACCESS_ONCE(rdp->qlen) = 0; - rdp->dynticks = &per_cpu(rcu_dynticks, cpu); - WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); - WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); - rdp->cpu = cpu; - rdp->rsp = rsp; - rcu_boot_init_nocb_percpu_data(rdp); - raw_spin_unlock_irqrestore(&rnp->lock, flags); -} - -/* - * Initialize a CPU's per-CPU RCU data. Note that only one online or - * offline event can be happening at a given time. Note also that we - * can accept some slop in the rsp->completed access due to the fact - * that this CPU cannot possibly have any RCU callbacks in flight yet. - */ -static void -rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) -{ - unsigned long flags; - unsigned long mask; - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_node *rnp = rcu_get_root(rsp); - - /* Exclude new grace periods. */ - mutex_lock(&rsp->onoff_mutex); - - /* Set up local state, ensuring consistent view of global state. */ - raw_spin_lock_irqsave(&rnp->lock, flags); - rdp->beenonline = 1; /* We have now been online. */ - rdp->preemptible = preemptible; - rdp->qlen_last_fqs_check = 0; - rdp->n_force_qs_snap = rsp->n_force_qs; - rdp->blimit = blimit; - init_callback_list(rdp); /* Re-enable callbacks on this CPU. */ - rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; - rcu_sysidle_init_percpu_data(rdp->dynticks); - atomic_set(&rdp->dynticks->dynticks, - (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - - /* Add CPU to rcu_node bitmasks. */ - rnp = rdp->mynode; - mask = rdp->grpmask; - do { - /* Exclude any attempts to start a new GP on small systems. */ - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rnp->qsmaskinit |= mask; - mask = rnp->grpmask; - if (rnp == rdp->mynode) { - /* - * If there is a grace period in progress, we will - * set up to wait for it next time we run the - * RCU core code. - */ - rdp->gpnum = rnp->completed; - rdp->completed = rnp->completed; - rdp->passed_quiesce = 0; - rdp->qs_pending = 0; - trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl")); - } - raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ - rnp = rnp->parent; - } while (rnp != NULL && !(rnp->qsmaskinit & mask)); - local_irq_restore(flags); - - mutex_unlock(&rsp->onoff_mutex); -} - -static void rcu_prepare_cpu(int cpu) -{ - struct rcu_state *rsp; - - for_each_rcu_flavor(rsp) - rcu_init_percpu_data(cpu, rsp, - strcmp(rsp->name, "rcu_preempt") == 0); -} - -/* - * Handle CPU online/offline notification events. - */ -static int rcu_cpu_notify(struct notifier_block *self, - unsigned long action, void *hcpu) -{ - long cpu = (long)hcpu; - struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); - struct rcu_node *rnp = rdp->mynode; - struct rcu_state *rsp; - - trace_rcu_utilization(TPS("Start CPU hotplug")); - switch (action) { - case CPU_UP_PREPARE: - case CPU_UP_PREPARE_FROZEN: - rcu_prepare_cpu(cpu); - rcu_prepare_kthreads(cpu); - break; - case CPU_ONLINE: - case CPU_DOWN_FAILED: - rcu_boost_kthread_setaffinity(rnp, -1); - break; - case CPU_DOWN_PREPARE: - rcu_boost_kthread_setaffinity(rnp, cpu); - break; - case CPU_DYING: - case CPU_DYING_FROZEN: - for_each_rcu_flavor(rsp) - rcu_cleanup_dying_cpu(rsp); - break; - case CPU_DEAD: - case CPU_DEAD_FROZEN: - case CPU_UP_CANCELED: - case CPU_UP_CANCELED_FROZEN: - for_each_rcu_flavor(rsp) - rcu_cleanup_dead_cpu(cpu, rsp); - break; - default: - break; - } - trace_rcu_utilization(TPS("End CPU hotplug")); - return NOTIFY_OK; -} - -static int rcu_pm_notify(struct notifier_block *self, - unsigned long action, void *hcpu) -{ - switch (action) { - case PM_HIBERNATION_PREPARE: - case PM_SUSPEND_PREPARE: - if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ - rcu_expedited = 1; - break; - case PM_POST_HIBERNATION: - case PM_POST_SUSPEND: - rcu_expedited = 0; - break; - default: - break; - } - return NOTIFY_OK; -} - -/* - * Spawn the kthread that handles this RCU flavor's grace periods. - */ -static int __init rcu_spawn_gp_kthread(void) -{ - unsigned long flags; - struct rcu_node *rnp; - struct rcu_state *rsp; - struct task_struct *t; - - for_each_rcu_flavor(rsp) { - t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name); - BUG_ON(IS_ERR(t)); - rnp = rcu_get_root(rsp); - raw_spin_lock_irqsave(&rnp->lock, flags); - rsp->gp_kthread = t; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - rcu_spawn_nocb_kthreads(rsp); - } - return 0; -} -early_initcall(rcu_spawn_gp_kthread); - -/* - * This function is invoked towards the end of the scheduler's initialization - * process. Before this is called, the idle task might contain - * RCU read-side critical sections (during which time, this idle - * task is booting the system). After this function is called, the - * idle tasks are prohibited from containing RCU read-side critical - * sections. This function also enables RCU lockdep checking. - */ -void rcu_scheduler_starting(void) -{ - WARN_ON(num_online_cpus() != 1); - WARN_ON(nr_context_switches() > 0); - rcu_scheduler_active = 1; -} - -/* - * Compute the per-level fanout, either using the exact fanout specified - * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. - */ -#ifdef CONFIG_RCU_FANOUT_EXACT -static void __init rcu_init_levelspread(struct rcu_state *rsp) -{ - int i; - - for (i = rcu_num_lvls - 1; i > 0; i--) - rsp->levelspread[i] = CONFIG_RCU_FANOUT; - rsp->levelspread[0] = rcu_fanout_leaf; -} -#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ -static void __init rcu_init_levelspread(struct rcu_state *rsp) -{ - int ccur; - int cprv; - int i; - - cprv = nr_cpu_ids; - for (i = rcu_num_lvls - 1; i >= 0; i--) { - ccur = rsp->levelcnt[i]; - rsp->levelspread[i] = (cprv + ccur - 1) / ccur; - cprv = ccur; - } -} -#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ - -/* - * Helper function for rcu_init() that initializes one rcu_state structure. - */ -static void __init rcu_init_one(struct rcu_state *rsp, - struct rcu_data __percpu *rda) -{ - static char *buf[] = { "rcu_node_0", - "rcu_node_1", - "rcu_node_2", - "rcu_node_3" }; /* Match MAX_RCU_LVLS */ - static char *fqs[] = { "rcu_node_fqs_0", - "rcu_node_fqs_1", - "rcu_node_fqs_2", - "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ - int cpustride = 1; - int i; - int j; - struct rcu_node *rnp; - - BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ - - /* Silence gcc 4.8 warning about array index out of range. */ - if (rcu_num_lvls > RCU_NUM_LVLS) - panic("rcu_init_one: rcu_num_lvls overflow"); - - /* Initialize the level-tracking arrays. */ - - for (i = 0; i < rcu_num_lvls; i++) - rsp->levelcnt[i] = num_rcu_lvl[i]; - for (i = 1; i < rcu_num_lvls; i++) - rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; - rcu_init_levelspread(rsp); - - /* Initialize the elements themselves, starting from the leaves. */ - - for (i = rcu_num_lvls - 1; i >= 0; i--) { - cpustride *= rsp->levelspread[i]; - rnp = rsp->level[i]; - for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { - raw_spin_lock_init(&rnp->lock); - lockdep_set_class_and_name(&rnp->lock, - &rcu_node_class[i], buf[i]); - raw_spin_lock_init(&rnp->fqslock); - lockdep_set_class_and_name(&rnp->fqslock, - &rcu_fqs_class[i], fqs[i]); - rnp->gpnum = rsp->gpnum; - rnp->completed = rsp->completed; - rnp->qsmask = 0; - rnp->qsmaskinit = 0; - rnp->grplo = j * cpustride; - rnp->grphi = (j + 1) * cpustride - 1; - if (rnp->grphi >= NR_CPUS) - rnp->grphi = NR_CPUS - 1; - if (i == 0) { - rnp->grpnum = 0; - rnp->grpmask = 0; - rnp->parent = NULL; - } else { - rnp->grpnum = j % rsp->levelspread[i - 1]; - rnp->grpmask = 1UL << rnp->grpnum; - rnp->parent = rsp->level[i - 1] + - j / rsp->levelspread[i - 1]; - } - rnp->level = i; - INIT_LIST_HEAD(&rnp->blkd_tasks); - rcu_init_one_nocb(rnp); - } - } - - rsp->rda = rda; - init_waitqueue_head(&rsp->gp_wq); - init_irq_work(&rsp->wakeup_work, rsp_wakeup); - rnp = rsp->level[rcu_num_lvls - 1]; - for_each_possible_cpu(i) { - while (i > rnp->grphi) - rnp++; - per_cpu_ptr(rsp->rda, i)->mynode = rnp; - rcu_boot_init_percpu_data(i, rsp); - } - list_add(&rsp->flavors, &rcu_struct_flavors); -} - -/* - * Compute the rcu_node tree geometry from kernel parameters. This cannot - * replace the definitions in rcutree.h because those are needed to size - * the ->node array in the rcu_state structure. - */ -static void __init rcu_init_geometry(void) -{ - ulong d; - int i; - int j; - int n = nr_cpu_ids; - int rcu_capacity[MAX_RCU_LVLS + 1]; - - /* - * Initialize any unspecified boot parameters. - * The default values of jiffies_till_first_fqs and - * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS - * value, which is a function of HZ, then adding one for each - * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. - */ - d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; - if (jiffies_till_first_fqs == ULONG_MAX) - jiffies_till_first_fqs = d; - if (jiffies_till_next_fqs == ULONG_MAX) - jiffies_till_next_fqs = d; - - /* If the compile-time values are accurate, just leave. */ - if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF && - nr_cpu_ids == NR_CPUS) - return; - - /* - * Compute number of nodes that can be handled an rcu_node tree - * with the given number of levels. Setting rcu_capacity[0] makes - * some of the arithmetic easier. - */ - rcu_capacity[0] = 1; - rcu_capacity[1] = rcu_fanout_leaf; - for (i = 2; i <= MAX_RCU_LVLS; i++) - rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; - - /* - * The boot-time rcu_fanout_leaf parameter is only permitted - * to increase the leaf-level fanout, not decrease it. Of course, - * the leaf-level fanout cannot exceed the number of bits in - * the rcu_node masks. Finally, the tree must be able to accommodate - * the configured number of CPUs. Complain and fall back to the - * compile-time values if these limits are exceeded. - */ - if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || - rcu_fanout_leaf > sizeof(unsigned long) * 8 || - n > rcu_capacity[MAX_RCU_LVLS]) { - WARN_ON(1); - return; - } - - /* Calculate the number of rcu_nodes at each level of the tree. */ - for (i = 1; i <= MAX_RCU_LVLS; i++) - if (n <= rcu_capacity[i]) { - for (j = 0; j <= i; j++) - num_rcu_lvl[j] = - DIV_ROUND_UP(n, rcu_capacity[i - j]); - rcu_num_lvls = i; - for (j = i + 1; j <= MAX_RCU_LVLS; j++) - num_rcu_lvl[j] = 0; - break; - } - - /* Calculate the total number of rcu_node structures. */ - rcu_num_nodes = 0; - for (i = 0; i <= MAX_RCU_LVLS; i++) - rcu_num_nodes += num_rcu_lvl[i]; - rcu_num_nodes -= n; -} - -void __init rcu_init(void) -{ - int cpu; - - rcu_bootup_announce(); - rcu_init_geometry(); - rcu_init_one(&rcu_sched_state, &rcu_sched_data); - rcu_init_one(&rcu_bh_state, &rcu_bh_data); - __rcu_init_preempt(); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); - - /* - * We don't need protection against CPU-hotplug here because - * this is called early in boot, before either interrupts - * or the scheduler are operational. - */ - cpu_notifier(rcu_cpu_notify, 0); - pm_notifier(rcu_pm_notify, 0); - for_each_online_cpu(cpu) - rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); -} - -#include "rcutree_plugin.h" |