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authorThomas Gleixner <tglx@linutronix.de>2011-10-05 11:59:38 -0700
committerClark Williams <williams@redhat.com>2012-04-13 11:01:42 -0500
commitd9e16f364c30463714ccb9789dd38bd4057c28fd (patch)
treeb49d18677035e81dfea8f840c9538af995d334d9 /include/linux/rcupdate.h
parent33e7935c81c659618b7f4dc5a98b62f3d3136587 (diff)
rcu: Merge RCU-bh into RCU-preempt
The Linux kernel has long RCU-bh read-side critical sections that intolerably increase scheduling latency under mainline's RCU-bh rules, which include RCU-bh read-side critical sections being non-preemptible. This patch therefore arranges for RCU-bh to be implemented in terms of RCU-preempt for CONFIG_PREEMPT_RT_FULL=y. This has the downside of defeating the purpose of RCU-bh, namely, handling the case where the system is subjected to a network-based denial-of-service attack that keeps at least one CPU doing full-time softirq processing. This issue will be fixed by a later commit. The current commit will need some work to make it appropriate for mainline use, for example, it needs to be extended to cover Tiny RCU. [ paulmck: Added a useful changelog ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/20111005185938.GA20403@linux.vnet.ibm.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h25
1 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 23a500f70fcf..888d24ac66ba 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -101,6 +101,9 @@ extern void call_rcu(struct rcu_head *head,
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
+#ifdef CONFIG_PREEMPT_RT_FULL
+#define call_rcu_bh call_rcu
+#else
/**
* call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.
* @head: structure to be used for queueing the RCU updates.
@@ -121,6 +124,7 @@ extern void call_rcu(struct rcu_head *head,
*/
extern void call_rcu_bh(struct rcu_head *head,
void (*func)(struct rcu_head *head));
+#endif
/**
* call_rcu_sched() - Queue an RCU for invocation after sched grace period.
@@ -190,7 +194,13 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
extern void rcu_sched_qs(int cpu);
+
+#ifndef CONFIG_PREEMPT_RT_FULL
extern void rcu_bh_qs(int cpu);
+#else
+static inline void rcu_bh_qs(int cpu) { }
+#endif
+
extern void rcu_check_callbacks(int cpu, int user);
struct notifier_block;
extern void rcu_idle_enter(void);
@@ -331,7 +341,14 @@ static inline int rcu_read_lock_held(void)
* rcu_read_lock_bh_held() is defined out of line to avoid #include-file
* hell.
*/
+#ifdef CONFIG_PREEMPT_RT_FULL
+static inline int rcu_read_lock_bh_held(void)
+{
+ return rcu_read_lock_held();
+}
+#else
extern int rcu_read_lock_bh_held(void);
+#endif
/**
* rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
@@ -780,10 +797,14 @@ static inline void rcu_read_unlock(void)
static inline void rcu_read_lock_bh(void)
{
local_bh_disable();
+#ifdef CONFIG_PREEMPT_RT_FULL
+ rcu_read_lock();
+#else
__acquire(RCU_BH);
rcu_lock_acquire(&rcu_bh_lock_map);
rcu_lockdep_assert(!rcu_is_cpu_idle(),
"rcu_read_lock_bh() used illegally while idle");
+#endif
}
/*
@@ -793,10 +814,14 @@ static inline void rcu_read_lock_bh(void)
*/
static inline void rcu_read_unlock_bh(void)
{
+#ifdef CONFIG_PREEMPT_RT_FULL
+ rcu_read_unlock();
+#else
rcu_lockdep_assert(!rcu_is_cpu_idle(),
"rcu_read_unlock_bh() used illegally while idle");
rcu_lock_release(&rcu_bh_lock_map);
__release(RCU_BH);
+#endif
local_bh_enable();
}