rt: Add the preempt-rt lock replacement APIs

Map spinlocks, rwlocks, rw_semaphores and semaphores to the rt_mutex
based locking functions for preempt-rt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 456 insertions, 2 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index e898c5b9d02c..c961d3abfe4c 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -7,8 +7,8 @@ obj-y     = sched.o fork.o exec_domain.o panic.o printk.o \
 	    sysctl.o sysctl_binary.o capability.o ptrace.o timer.o user.o \
 	    signal.o sys.o kmod.o workqueue.o pid.o \
 	    rcupdate.o extable.o params.o posix-timers.o \
-	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
-	    hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
+	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o \
+	    hrtimer.o nsproxy.o srcu.o semaphore.o \
 	    notifier.o ksysfs.o sched_clock.o cred.o \
 	    async.o range.o
 obj-y += groups.o
@@ -29,7 +29,11 @@ obj-$(CONFIG_PROFILING) += profile.o
 obj-$(CONFIG_SYSCTL_SYSCALL_CHECK) += sysctl_check.o
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
 obj-y += time/
+ifneq ($(CONFIG_PREEMPT_RT_FULL),y)
+obj-y += mutex.o
 obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o
+obj-y += rwsem.o
+endif
 obj-$(CONFIG_LOCKDEP) += lockdep.o
 ifeq ($(CONFIG_PROC_FS),y)
 obj-$(CONFIG_LOCKDEP) += lockdep_proc.o
@@ -41,6 +45,7 @@ endif
 obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
 obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
 obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
+obj-$(CONFIG_PREEMPT_RT_FULL) += rt.o
 obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
 obj-$(CONFIG_SMP) += smp.o
 ifneq ($(CONFIG_SMP),y)
diff --git a/kernel/rt.c b/kernel/rt.c
new file mode 100644
index 000000000000..092d6b356d59
--- /dev/null
+++ b/kernel/rt.c
@@ -0,0 +1,442 @@
+/*
+ * kernel/rt.c
+ *
+ * Real-Time Preemption Support
+ *
+ * started by Ingo Molnar:
+ *
+ *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ *
+ * historic credit for proving that Linux spinlocks can be implemented via
+ * RT-aware mutexes goes to many people: The Pmutex project (Dirk Grambow
+ * and others) who prototyped it on 2.4 and did lots of comparative
+ * research and analysis; TimeSys, for proving that you can implement a
+ * fully preemptible kernel via the use of IRQ threading and mutexes;
+ * Bill Huey for persuasively arguing on lkml that the mutex model is the
+ * right one; and to MontaVista, who ported pmutexes to 2.6.
+ *
+ * This code is a from-scratch implementation and is not based on pmutexes,
+ * but the idea of converting spinlocks to mutexes is used here too.
+ *
+ * lock debugging, locking tree, deadlock detection:
+ *
+ *  Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey
+ *  Released under the General Public License (GPL).
+ *
+ * Includes portions of the generic R/W semaphore implementation from:
+ *
+ *  Copyright (c) 2001   David Howells (dhowells@redhat.com).
+ *  - Derived partially from idea by Andrea Arcangeli <andrea@suse.de>
+ *  - Derived also from comments by Linus
+ *
+ * Pending ownership of locks and ownership stealing:
+ *
+ *  Copyright (C) 2005, Kihon Technologies Inc., Steven Rostedt
+ *
+ *   (also by Steven Rostedt)
+ *    - Converted single pi_lock to individual task locks.
+ *
+ * By Esben Nielsen:
+ *    Doing priority inheritance with help of the scheduler.
+ *
+ *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ *  - major rework based on Esben Nielsens initial patch
+ *  - replaced thread_info references by task_struct refs
+ *  - removed task->pending_owner dependency
+ *  - BKL drop/reacquire for semaphore style locks to avoid deadlocks
+ *    in the scheduler return path as discussed with Steven Rostedt
+ *
+ *  Copyright (C) 2006, Kihon Technologies Inc.
+ *    Steven Rostedt <rostedt@goodmis.org>
+ *  - debugged and patched Thomas Gleixner's rework.
+ *  - added back the cmpxchg to the rework.
+ *  - turned atomic require back on for SMP.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/rtmutex.h>
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+#include <linux/syscalls.h>
+#include <linux/interrupt.h>
+#include <linux/plist.h>
+#include <linux/fs.h>
+#include <linux/futex.h>
+#include <linux/hrtimer.h>
+
+#include "rtmutex_common.h"
+
+/*
+ * struct mutex functions
+ */
+void __mutex_do_init(struct mutex *mutex, const char *name,
+		     struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	/*
+	 * Make sure we are not reinitializing a held lock:
+	 */
+	debug_check_no_locks_freed((void *)mutex, sizeof(*mutex));
+	lockdep_init_map(&mutex->dep_map, name, key, 0);
+#endif
+	mutex->lock.save_state = 0;
+}
+EXPORT_SYMBOL(__mutex_do_init);
+
+void __lockfunc _mutex_lock(struct mutex *lock)
+{
+	mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
+	rt_mutex_lock(&lock->lock);
+}
+EXPORT_SYMBOL(_mutex_lock);
+
+int __lockfunc _mutex_lock_interruptible(struct mutex *lock)
+{
+	int ret;
+
+	mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
+	ret = rt_mutex_lock_interruptible(&lock->lock, 0);
+	if (ret)
+		mutex_release(&lock->dep_map, 1, _RET_IP_);
+	return ret;
+}
+EXPORT_SYMBOL(_mutex_lock_interruptible);
+
+int __lockfunc _mutex_lock_killable(struct mutex *lock)
+{
+	int ret;
+
+	mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
+	ret = rt_mutex_lock_killable(&lock->lock, 0);
+	if (ret)
+		mutex_release(&lock->dep_map, 1, _RET_IP_);
+	return ret;
+}
+EXPORT_SYMBOL(_mutex_lock_killable);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+void __lockfunc _mutex_lock_nested(struct mutex *lock, int subclass)
+{
+	mutex_acquire_nest(&lock->dep_map, subclass, 0, NULL, _RET_IP_);
+	rt_mutex_lock(&lock->lock);
+}
+EXPORT_SYMBOL(_mutex_lock_nested);
+
+void __lockfunc _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
+{
+	mutex_acquire_nest(&lock->dep_map, 0, 0, nest, _RET_IP_);
+	rt_mutex_lock(&lock->lock);
+}
+EXPORT_SYMBOL(_mutex_lock_nest_lock);
+
+int __lockfunc _mutex_lock_interruptible_nested(struct mutex *lock, int subclass)
+{
+	int ret;
+
+	mutex_acquire_nest(&lock->dep_map, subclass, 0, NULL, _RET_IP_);
+	ret = rt_mutex_lock_interruptible(&lock->lock, 0);
+	if (ret)
+		mutex_release(&lock->dep_map, 1, _RET_IP_);
+	return ret;
+}
+EXPORT_SYMBOL(_mutex_lock_interruptible_nested);
+
+int __lockfunc _mutex_lock_killable_nested(struct mutex *lock, int subclass)
+{
+	int ret;
+
+	mutex_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
+	ret = rt_mutex_lock_killable(&lock->lock, 0);
+	if (ret)
+		mutex_release(&lock->dep_map, 1, _RET_IP_);
+	return ret;
+}
+EXPORT_SYMBOL(_mutex_lock_killable_nested);
+#endif
+
+int __lockfunc _mutex_trylock(struct mutex *lock)
+{
+	int ret = rt_mutex_trylock(&lock->lock);
+
+	if (ret)
+		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+
+	return ret;
+}
+EXPORT_SYMBOL(_mutex_trylock);
+
+void __lockfunc _mutex_unlock(struct mutex *lock)
+{
+	mutex_release(&lock->dep_map, 1, _RET_IP_);
+	rt_mutex_unlock(&lock->lock);
+}
+EXPORT_SYMBOL(_mutex_unlock);
+
+/*
+ * rwlock_t functions
+ */
+int __lockfunc rt_write_trylock(rwlock_t *rwlock)
+{
+	int ret = rt_mutex_trylock(&rwlock->lock);
+
+	migrate_disable();
+	if (ret)
+		rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
+	else
+		migrate_enable();
+
+	return ret;
+}
+EXPORT_SYMBOL(rt_write_trylock);
+
+int __lockfunc rt_write_trylock_irqsave(rwlock_t *rwlock, unsigned long *flags)
+{
+	int ret;
+
+	*flags = 0;
+	migrate_disable();
+	ret = rt_write_trylock(rwlock);
+	if (!ret)
+		migrate_enable();
+	return ret;
+}
+EXPORT_SYMBOL(rt_write_trylock_irqsave);
+
+int __lockfunc rt_read_trylock(rwlock_t *rwlock)
+{
+	struct rt_mutex *lock = &rwlock->lock;
+	int ret = 1;
+
+	/*
+	 * recursive read locks succeed when current owns the lock,
+	 * but not when read_depth == 0 which means that the lock is
+	 * write locked.
+	 */
+	migrate_disable();
+	if (rt_mutex_owner(lock) != current)
+		ret = rt_mutex_trylock(lock);
+	else if (!rwlock->read_depth)
+		ret = 0;
+
+	if (ret) {
+		rwlock->read_depth++;
+		rwlock_acquire_read(&rwlock->dep_map, 0, 1, _RET_IP_);
+	} else
+		migrate_enable();
+
+	return ret;
+}
+EXPORT_SYMBOL(rt_read_trylock);
+
+void __lockfunc rt_write_lock(rwlock_t *rwlock)
+{
+	rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
+	__rt_spin_lock(&rwlock->lock);
+}
+EXPORT_SYMBOL(rt_write_lock);
+
+void __lockfunc rt_read_lock(rwlock_t *rwlock)
+{
+	struct rt_mutex *lock = &rwlock->lock;
+
+	rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
+
+	/*
+	 * recursive read locks succeed when current owns the lock
+	 */
+	if (rt_mutex_owner(lock) != current)
+		__rt_spin_lock(lock);
+	rwlock->read_depth++;
+}
+
+EXPORT_SYMBOL(rt_read_lock);
+
+void __lockfunc rt_write_unlock(rwlock_t *rwlock)
+{
+	/* NOTE: we always pass in '1' for nested, for simplicity */
+	rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
+	__rt_spin_unlock(&rwlock->lock);
+}
+EXPORT_SYMBOL(rt_write_unlock);
+
+void __lockfunc rt_read_unlock(rwlock_t *rwlock)
+{
+	rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
+
+	/* Release the lock only when read_depth is down to 0 */
+	if (--rwlock->read_depth == 0)
+		__rt_spin_unlock(&rwlock->lock);
+}
+EXPORT_SYMBOL(rt_read_unlock);
+
+unsigned long __lockfunc rt_write_lock_irqsave(rwlock_t *rwlock)
+{
+	rt_write_lock(rwlock);
+
+	return 0;
+}
+EXPORT_SYMBOL(rt_write_lock_irqsave);
+
+unsigned long __lockfunc rt_read_lock_irqsave(rwlock_t *rwlock)
+{
+	rt_read_lock(rwlock);
+
+	return 0;
+}
+EXPORT_SYMBOL(rt_read_lock_irqsave);
+
+void __rt_rwlock_init(rwlock_t *rwlock, char *name, struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	/*
+	 * Make sure we are not reinitializing a held lock:
+	 */
+	debug_check_no_locks_freed((void *)rwlock, sizeof(*rwlock));
+	lockdep_init_map(&rwlock->dep_map, name, key, 0);
+#endif
+	rwlock->lock.save_state = 1;
+	rwlock->read_depth = 0;
+}
+EXPORT_SYMBOL(__rt_rwlock_init);
+
+/*
+ * rw_semaphores
+ */
+
+void  rt_up_write(struct rw_semaphore *rwsem)
+{
+	rwsem_release(&rwsem->dep_map, 1, _RET_IP_);
+	rt_mutex_unlock(&rwsem->lock);
+}
+EXPORT_SYMBOL(rt_up_write);
+
+void  rt_up_read(struct rw_semaphore *rwsem)
+{
+	rwsem_release(&rwsem->dep_map, 1, _RET_IP_);
+	if (--rwsem->read_depth == 0)
+		rt_mutex_unlock(&rwsem->lock);
+}
+EXPORT_SYMBOL(rt_up_read);
+
+/*
+ * downgrade a write lock into a read lock
+ * - just wake up any readers at the front of the queue
+ */
+void  rt_downgrade_write(struct rw_semaphore *rwsem)
+{
+	BUG_ON(rt_mutex_owner(&rwsem->lock) != current);
+	rwsem->read_depth = 1;
+}
+EXPORT_SYMBOL(rt_downgrade_write);
+
+int  rt_down_write_trylock(struct rw_semaphore *rwsem)
+{
+	int ret = rt_mutex_trylock(&rwsem->lock);
+
+	if (ret)
+		rwsem_acquire(&rwsem->dep_map, 0, 1, _RET_IP_);
+	return ret;
+}
+EXPORT_SYMBOL(rt_down_write_trylock);
+
+void  rt_down_write(struct rw_semaphore *rwsem)
+{
+	rwsem_acquire(&rwsem->dep_map, 0, 0, _RET_IP_);
+	rt_mutex_lock(&rwsem->lock);
+}
+EXPORT_SYMBOL(rt_down_write);
+
+void  rt_down_write_nested(struct rw_semaphore *rwsem, int subclass)
+{
+	rwsem_acquire(&rwsem->dep_map, subclass, 0, _RET_IP_);
+	rt_mutex_lock(&rwsem->lock);
+}
+EXPORT_SYMBOL(rt_down_write_nested);
+
+int  rt_down_read_trylock(struct rw_semaphore *rwsem)
+{
+	struct rt_mutex *lock = &rwsem->lock;
+	int ret = 1;
+
+	/*
+	 * recursive read locks succeed when current owns the rwsem,
+	 * but not when read_depth == 0 which means that the rwsem is
+	 * write locked.
+	 */
+	if (rt_mutex_owner(lock) != current)
+		ret = rt_mutex_trylock(&rwsem->lock);
+	else if (!rwsem->read_depth)
+		ret = 0;
+
+	if (ret) {
+		rwsem->read_depth++;
+		rwsem_acquire(&rwsem->dep_map, 0, 1, _RET_IP_);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(rt_down_read_trylock);
+
+static void __rt_down_read(struct rw_semaphore *rwsem, int subclass)
+{
+	struct rt_mutex *lock = &rwsem->lock;
+
+	rwsem_acquire_read(&rwsem->dep_map, subclass, 0, _RET_IP_);
+
+	if (rt_mutex_owner(lock) != current)
+		rt_mutex_lock(&rwsem->lock);
+	rwsem->read_depth++;
+}
+
+void  rt_down_read(struct rw_semaphore *rwsem)
+{
+	__rt_down_read(rwsem, 0);
+}
+EXPORT_SYMBOL(rt_down_read);
+
+void  rt_down_read_nested(struct rw_semaphore *rwsem, int subclass)
+{
+	__rt_down_read(rwsem, subclass);
+}
+EXPORT_SYMBOL(rt_down_read_nested);
+
+void  __rt_rwsem_init(struct rw_semaphore *rwsem, char *name,
+			      struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	/*
+	 * Make sure we are not reinitializing a held lock:
+	 */
+	debug_check_no_locks_freed((void *)rwsem, sizeof(*rwsem));
+	lockdep_init_map(&rwsem->dep_map, name, key, 0);
+#endif
+	rwsem->read_depth = 0;
+	rwsem->lock.save_state = 0;
+}
+EXPORT_SYMBOL(__rt_rwsem_init);
+
+/**
+ * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
+ * @cnt: the atomic which we are to dec
+ * @lock: the mutex to return holding if we dec to 0
+ *
+ * return true and hold lock if we dec to 0, return false otherwise
+ */
+int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
+{
+	/* dec if we can't possibly hit 0 */
+	if (atomic_add_unless(cnt, -1, 1))
+		return 0;
+	/* we might hit 0, so take the lock */
+	mutex_lock(lock);
+	if (!atomic_dec_and_test(cnt)) {
+		/* when we actually did the dec, we didn't hit 0 */
+		mutex_unlock(lock);
+		return 0;
+	}
+	/* we hit 0, and we hold the lock */
+	return 1;
+}
+EXPORT_SYMBOL(atomic_dec_and_mutex_lock);
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index 84c7d96918bf..47fd3cf03a8e 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -110,8 +110,11 @@ void __lockfunc __raw_##op##_lock_bh(locktype##_t *lock)		\
  *         __[spin|read|write]_lock_bh()
  */
 BUILD_LOCK_OPS(spin, raw_spinlock);
+
+#ifndef CONFIG_PREEMPT_RT_FULL
 BUILD_LOCK_OPS(read, rwlock);
 BUILD_LOCK_OPS(write, rwlock);
+#endif
 
 #endif
 
@@ -195,6 +198,8 @@ void __lockfunc _raw_spin_unlock_bh(raw_spinlock_t *lock)
 EXPORT_SYMBOL(_raw_spin_unlock_bh);
 #endif
 
+#ifndef CONFIG_PREEMPT_RT_FULL
+
 #ifndef CONFIG_INLINE_READ_TRYLOCK
 int __lockfunc _raw_read_trylock(rwlock_t *lock)
 {
@@ -339,6 +344,8 @@ void __lockfunc _raw_write_unlock_bh(rwlock_t *lock)
 EXPORT_SYMBOL(_raw_write_unlock_bh);
 #endif
 
+#endif /* !PREEMPT_RT_FULL */
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
 void __lockfunc _raw_spin_lock_nested(raw_spinlock_t *lock, int subclass)