Suggested-by: Ingo Molnar Signed-off-by: Peter Zijlstra --- kernel/Makefile | 6 kernel/locking/Makefile | 9 kernel/locking/mutex-debug.c | 110 ++++ kernel/locking/mutex-debug.h | 55 ++ kernel/locking/mutex.c | 960 +++++++++++++++++++++++++++++++++++++++++++ kernel/locking/mutex.h | 48 ++ kernel/mutex-debug.c | 110 ---- kernel/mutex-debug.h | 55 -- kernel/mutex.c | 960 ------------------------------------------- kernel/mutex.h | 48 -- 10 files changed, 1184 insertions(+), 1177 deletions(-) Index: linux-2.6/kernel/Makefile =================================================================== --- linux-2.6.orig/kernel/Makefile +++ linux-2.6/kernel/Makefile @@ -7,7 +7,7 @@ obj-y = fork.o exec_domain.o panic.o sysctl.o sysctl_binary.o capability.o ptrace.o timer.o user.o \ signal.o sys.o kmod.o workqueue.o pid.o task_work.o \ extable.o params.o posix-timers.o \ - kthread.o sys_ni.o posix-cpu-timers.o mutex.o \ + kthread.o sys_ni.o posix-cpu-timers.o \ hrtimer.o rwsem.o nsproxy.o semaphore.o \ notifier.o ksysfs.o cred.o reboot.o \ async.o range.o groups.o lglock.o smpboot.o @@ -16,13 +16,12 @@ ifdef CONFIG_FUNCTION_TRACER # Do not trace debug files and internal ftrace files CFLAGS_REMOVE_lockdep.o = -pg CFLAGS_REMOVE_lockdep_proc.o = -pg -CFLAGS_REMOVE_mutex-debug.o = -pg -CFLAGS_REMOVE_rtmutex-debug.o = -pg CFLAGS_REMOVE_cgroup-debug.o = -pg CFLAGS_REMOVE_irq_work.o = -pg endif obj-y += sched/ +obj-y += locking/ obj-y += power/ obj-y += printk/ obj-y += cpu/ @@ -34,7 +33,6 @@ obj-$(CONFIG_FREEZER) += freezer.o obj-$(CONFIG_PROFILING) += profile.o obj-$(CONFIG_STACKTRACE) += stacktrace.o obj-y += time/ -obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o obj-$(CONFIG_LOCKDEP) += lockdep.o ifeq ($(CONFIG_PROC_FS),y) obj-$(CONFIG_LOCKDEP) += lockdep_proc.o Index: linux-2.6/kernel/locking/Makefile =================================================================== --- /dev/null +++ linux-2.6/kernel/locking/Makefile @@ -0,0 +1,9 @@ + +obj-y += mutex.o + +ifdef CONFIG_FUNCTION_TRACER +CFLAGS_REMOVE_mutex-debug.o = -pg +CFLAGS_REMOVE_rtmutex-debug.o = -pg +endif + +obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o Index: linux-2.6/kernel/locking/mutex-debug.c =================================================================== --- /dev/null +++ linux-2.6/kernel/locking/mutex-debug.c @@ -0,0 +1,110 @@ +/* + * kernel/mutex-debug.c + * + * Debugging code for mutexes + * + * Started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar + * + * lock debugging, locking tree, deadlock detection started by: + * + * Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey + * Released under the General Public License (GPL). + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "mutex-debug.h" + +/* + * Must be called with lock->wait_lock held. + */ +void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter) +{ + memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter)); + waiter->magic = waiter; + INIT_LIST_HEAD(&waiter->list); +} + +void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter) +{ + SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock)); + DEBUG_LOCKS_WARN_ON(list_empty(&lock->wait_list)); + DEBUG_LOCKS_WARN_ON(waiter->magic != waiter); + DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list)); +} + +void debug_mutex_free_waiter(struct mutex_waiter *waiter) +{ + DEBUG_LOCKS_WARN_ON(!list_empty(&waiter->list)); + memset(waiter, MUTEX_DEBUG_FREE, sizeof(*waiter)); +} + +void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti) +{ + SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock)); + + /* Mark the current thread as blocked on the lock: */ + ti->task->blocked_on = waiter; +} + +void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti) +{ + DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list)); + DEBUG_LOCKS_WARN_ON(waiter->task != ti->task); + DEBUG_LOCKS_WARN_ON(ti->task->blocked_on != waiter); + ti->task->blocked_on = NULL; + + list_del_init(&waiter->list); + waiter->task = NULL; +} + +void debug_mutex_unlock(struct mutex *lock) +{ + if (unlikely(!debug_locks)) + return; + + DEBUG_LOCKS_WARN_ON(lock->magic != lock); + DEBUG_LOCKS_WARN_ON(lock->owner != current); + DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next); + mutex_clear_owner(lock); +} + +void debug_mutex_init(struct mutex *lock, 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 *)lock, sizeof(*lock)); + lockdep_init_map(&lock->dep_map, name, key, 0); +#endif + lock->magic = lock; +} + +/*** + * mutex_destroy - mark a mutex unusable + * @lock: the mutex to be destroyed + * + * This function marks the mutex uninitialized, and any subsequent + * use of the mutex is forbidden. The mutex must not be locked when + * this function is called. + */ +void mutex_destroy(struct mutex *lock) +{ + DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock)); + lock->magic = NULL; +} + +EXPORT_SYMBOL_GPL(mutex_destroy); Index: linux-2.6/kernel/locking/mutex-debug.h =================================================================== --- /dev/null +++ linux-2.6/kernel/locking/mutex-debug.h @@ -0,0 +1,55 @@ +/* + * Mutexes: blocking mutual exclusion locks + * + * started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar + * + * This file contains mutex debugging related internal declarations, + * prototypes and inline functions, for the CONFIG_DEBUG_MUTEXES case. + * More details are in kernel/mutex-debug.c. + */ + +/* + * This must be called with lock->wait_lock held. + */ +extern void debug_mutex_lock_common(struct mutex *lock, + struct mutex_waiter *waiter); +extern void debug_mutex_wake_waiter(struct mutex *lock, + struct mutex_waiter *waiter); +extern void debug_mutex_free_waiter(struct mutex_waiter *waiter); +extern void debug_mutex_add_waiter(struct mutex *lock, + struct mutex_waiter *waiter, + struct thread_info *ti); +extern void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti); +extern void debug_mutex_unlock(struct mutex *lock); +extern void debug_mutex_init(struct mutex *lock, const char *name, + struct lock_class_key *key); + +static inline void mutex_set_owner(struct mutex *lock) +{ + lock->owner = current; +} + +static inline void mutex_clear_owner(struct mutex *lock) +{ + lock->owner = NULL; +} + +#define spin_lock_mutex(lock, flags) \ + do { \ + struct mutex *l = container_of(lock, struct mutex, wait_lock); \ + \ + DEBUG_LOCKS_WARN_ON(in_interrupt()); \ + local_irq_save(flags); \ + arch_spin_lock(&(lock)->rlock.raw_lock);\ + DEBUG_LOCKS_WARN_ON(l->magic != l); \ + } while (0) + +#define spin_unlock_mutex(lock, flags) \ + do { \ + arch_spin_unlock(&(lock)->rlock.raw_lock); \ + local_irq_restore(flags); \ + preempt_check_resched(); \ + } while (0) Index: linux-2.6/kernel/locking/mutex.c =================================================================== --- /dev/null +++ linux-2.6/kernel/locking/mutex.c @@ -0,0 +1,960 @@ +/* + * kernel/mutex.c + * + * Mutexes: blocking mutual exclusion locks + * + * Started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar + * + * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and + * David Howells for suggestions and improvements. + * + * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline + * from the -rt tree, where it was originally implemented for rtmutexes + * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale + * and Sven Dietrich. + * + * Also see Documentation/mutex-design.txt. + */ +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * In the DEBUG case we are using the "NULL fastpath" for mutexes, + * which forces all calls into the slowpath: + */ +#ifdef CONFIG_DEBUG_MUTEXES +# include "mutex-debug.h" +# include +#else +# include "mutex.h" +# include +#endif + +/* + * A negative mutex count indicates that waiters are sleeping waiting for the + * mutex. + */ +#define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) + +void +__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) +{ + atomic_set(&lock->count, 1); + spin_lock_init(&lock->wait_lock); + INIT_LIST_HEAD(&lock->wait_list); + mutex_clear_owner(lock); +#ifdef CONFIG_MUTEX_SPIN_ON_OWNER + lock->spin_mlock = NULL; +#endif + + debug_mutex_init(lock, name, key); +} + +EXPORT_SYMBOL(__mutex_init); + +#ifndef CONFIG_DEBUG_LOCK_ALLOC +/* + * We split the mutex lock/unlock logic into separate fastpath and + * slowpath functions, to reduce the register pressure on the fastpath. + * We also put the fastpath first in the kernel image, to make sure the + * branch is predicted by the CPU as default-untaken. + */ +static __used noinline void __sched +__mutex_lock_slowpath(atomic_t *lock_count); + +/** + * mutex_lock - acquire the mutex + * @lock: the mutex to be acquired + * + * Lock the mutex exclusively for this task. If the mutex is not + * available right now, it will sleep until it can get it. + * + * The mutex must later on be released by the same task that + * acquired it. Recursive locking is not allowed. The task + * may not exit without first unlocking the mutex. Also, kernel + * memory where the mutex resides mutex must not be freed with + * the mutex still locked. The mutex must first be initialized + * (or statically defined) before it can be locked. memset()-ing + * the mutex to 0 is not allowed. + * + * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging + * checks that will enforce the restrictions and will also do + * deadlock debugging. ) + * + * This function is similar to (but not equivalent to) down(). + */ +void __sched mutex_lock(struct mutex *lock) +{ + might_sleep(); + /* + * The locking fastpath is the 1->0 transition from + * 'unlocked' into 'locked' state. + */ + __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); + mutex_set_owner(lock); +} + +EXPORT_SYMBOL(mutex_lock); +#endif + +#ifdef CONFIG_MUTEX_SPIN_ON_OWNER +/* + * In order to avoid a stampede of mutex spinners from acquiring the mutex + * more or less simultaneously, the spinners need to acquire a MCS lock + * first before spinning on the owner field. + * + * We don't inline mspin_lock() so that perf can correctly account for the + * time spent in this lock function. + */ +struct mspin_node { + struct mspin_node *next ; + int locked; /* 1 if lock acquired */ +}; +#define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock)) + +static noinline +void mspin_lock(struct mspin_node **lock, struct mspin_node *node) +{ + struct mspin_node *prev; + + /* Init node */ + node->locked = 0; + node->next = NULL; + + prev = xchg(lock, node); + if (likely(prev == NULL)) { + /* Lock acquired */ + node->locked = 1; + return; + } + ACCESS_ONCE(prev->next) = node; + smp_wmb(); + /* Wait until the lock holder passes the lock down */ + while (!ACCESS_ONCE(node->locked)) + arch_mutex_cpu_relax(); +} + +static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node) +{ + struct mspin_node *next = ACCESS_ONCE(node->next); + + if (likely(!next)) { + /* + * Release the lock by setting it to NULL + */ + if (cmpxchg(lock, node, NULL) == node) + return; + /* Wait until the next pointer is set */ + while (!(next = ACCESS_ONCE(node->next))) + arch_mutex_cpu_relax(); + } + ACCESS_ONCE(next->locked) = 1; + smp_wmb(); +} + +/* + * Mutex spinning code migrated from kernel/sched/core.c + */ + +static inline bool owner_running(struct mutex *lock, struct task_struct *owner) +{ + if (lock->owner != owner) + return false; + + /* + * Ensure we emit the owner->on_cpu, dereference _after_ checking + * lock->owner still matches owner, if that fails, owner might + * point to free()d memory, if it still matches, the rcu_read_lock() + * ensures the memory stays valid. + */ + barrier(); + + return owner->on_cpu; +} + +/* + * Look out! "owner" is an entirely speculative pointer + * access and not reliable. + */ +static noinline +int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) +{ + rcu_read_lock(); + while (owner_running(lock, owner)) { + if (need_resched()) + break; + + arch_mutex_cpu_relax(); + } + rcu_read_unlock(); + + /* + * We break out the loop above on need_resched() and when the + * owner changed, which is a sign for heavy contention. Return + * success only when lock->owner is NULL. + */ + return lock->owner == NULL; +} + +/* + * Initial check for entering the mutex spinning loop + */ +static inline int mutex_can_spin_on_owner(struct mutex *lock) +{ + struct task_struct *owner; + int retval = 1; + + rcu_read_lock(); + owner = ACCESS_ONCE(lock->owner); + if (owner) + retval = owner->on_cpu; + rcu_read_unlock(); + /* + * if lock->owner is not set, the mutex owner may have just acquired + * it and not set the owner yet or the mutex has been released. + */ + return retval; +} +#endif + +static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count); + +/** + * mutex_unlock - release the mutex + * @lock: the mutex to be released + * + * Unlock a mutex that has been locked by this task previously. + * + * This function must not be used in interrupt context. Unlocking + * of a not locked mutex is not allowed. + * + * This function is similar to (but not equivalent to) up(). + */ +void __sched mutex_unlock(struct mutex *lock) +{ + /* + * The unlocking fastpath is the 0->1 transition from 'locked' + * into 'unlocked' state: + */ +#ifndef CONFIG_DEBUG_MUTEXES + /* + * When debugging is enabled we must not clear the owner before time, + * the slow path will always be taken, and that clears the owner field + * after verifying that it was indeed current. + */ + mutex_clear_owner(lock); +#endif + __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); +} + +EXPORT_SYMBOL(mutex_unlock); + +/** + * ww_mutex_unlock - release the w/w mutex + * @lock: the mutex to be released + * + * Unlock a mutex that has been locked by this task previously with any of the + * ww_mutex_lock* functions (with or without an acquire context). It is + * forbidden to release the locks after releasing the acquire context. + * + * This function must not be used in interrupt context. Unlocking + * of a unlocked mutex is not allowed. + */ +void __sched ww_mutex_unlock(struct ww_mutex *lock) +{ + /* + * The unlocking fastpath is the 0->1 transition from 'locked' + * into 'unlocked' state: + */ + if (lock->ctx) { +#ifdef CONFIG_DEBUG_MUTEXES + DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); +#endif + if (lock->ctx->acquired > 0) + lock->ctx->acquired--; + lock->ctx = NULL; + } + +#ifndef CONFIG_DEBUG_MUTEXES + /* + * When debugging is enabled we must not clear the owner before time, + * the slow path will always be taken, and that clears the owner field + * after verifying that it was indeed current. + */ + mutex_clear_owner(&lock->base); +#endif + __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath); +} +EXPORT_SYMBOL(ww_mutex_unlock); + +static inline int __sched +__mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx) +{ + struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); + struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx); + + if (!hold_ctx) + return 0; + + if (unlikely(ctx == hold_ctx)) + return -EALREADY; + + if (ctx->stamp - hold_ctx->stamp <= LONG_MAX && + (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) { +#ifdef CONFIG_DEBUG_MUTEXES + DEBUG_LOCKS_WARN_ON(ctx->contending_lock); + ctx->contending_lock = ww; +#endif + return -EDEADLK; + } + + return 0; +} + +static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww, + struct ww_acquire_ctx *ww_ctx) +{ +#ifdef CONFIG_DEBUG_MUTEXES + /* + * If this WARN_ON triggers, you used ww_mutex_lock to acquire, + * but released with a normal mutex_unlock in this call. + * + * This should never happen, always use ww_mutex_unlock. + */ + DEBUG_LOCKS_WARN_ON(ww->ctx); + + /* + * Not quite done after calling ww_acquire_done() ? + */ + DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); + + if (ww_ctx->contending_lock) { + /* + * After -EDEADLK you tried to + * acquire a different ww_mutex? Bad! + */ + DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); + + /* + * You called ww_mutex_lock after receiving -EDEADLK, + * but 'forgot' to unlock everything else first? + */ + DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); + ww_ctx->contending_lock = NULL; + } + + /* + * Naughty, using a different class will lead to undefined behavior! + */ + DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); +#endif + ww_ctx->acquired++; +} + +/* + * after acquiring lock with fastpath or when we lost out in contested + * slowpath, set ctx and wake up any waiters so they can recheck. + * + * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set, + * as the fastpath and opportunistic spinning are disabled in that case. + */ +static __always_inline void +ww_mutex_set_context_fastpath(struct ww_mutex *lock, + struct ww_acquire_ctx *ctx) +{ + unsigned long flags; + struct mutex_waiter *cur; + + ww_mutex_lock_acquired(lock, ctx); + + lock->ctx = ctx; + + /* + * The lock->ctx update should be visible on all cores before + * the atomic read is done, otherwise contended waiters might be + * missed. The contended waiters will either see ww_ctx == NULL + * and keep spinning, or it will acquire wait_lock, add itself + * to waiter list and sleep. + */ + smp_mb(); /* ^^^ */ + + /* + * Check if lock is contended, if not there is nobody to wake up + */ + if (likely(atomic_read(&lock->base.count) == 0)) + return; + + /* + * Uh oh, we raced in fastpath, wake up everyone in this case, + * so they can see the new lock->ctx. + */ + spin_lock_mutex(&lock->base.wait_lock, flags); + list_for_each_entry(cur, &lock->base.wait_list, list) { + debug_mutex_wake_waiter(&lock->base, cur); + wake_up_process(cur->task); + } + spin_unlock_mutex(&lock->base.wait_lock, flags); +} + +/* + * Lock a mutex (possibly interruptible), slowpath: + */ +static __always_inline int __sched +__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, + struct lockdep_map *nest_lock, unsigned long ip, + struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) +{ + struct task_struct *task = current; + struct mutex_waiter waiter; + unsigned long flags; + int ret; + + preempt_disable(); + mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); + +#ifdef CONFIG_MUTEX_SPIN_ON_OWNER + /* + * Optimistic spinning. + * + * We try to spin for acquisition when we find that there are no + * pending waiters and the lock owner is currently running on a + * (different) CPU. + * + * The rationale is that if the lock owner is running, it is likely to + * release the lock soon. + * + * Since this needs the lock owner, and this mutex implementation + * doesn't track the owner atomically in the lock field, we need to + * track it non-atomically. + * + * We can't do this for DEBUG_MUTEXES because that relies on wait_lock + * to serialize everything. + * + * The mutex spinners are queued up using MCS lock so that only one + * spinner can compete for the mutex. However, if mutex spinning isn't + * going to happen, there is no point in going through the lock/unlock + * overhead. + */ + if (!mutex_can_spin_on_owner(lock)) + goto slowpath; + + for (;;) { + struct task_struct *owner; + struct mspin_node node; + + if (use_ww_ctx && ww_ctx->acquired > 0) { + struct ww_mutex *ww; + + ww = container_of(lock, struct ww_mutex, base); + /* + * If ww->ctx is set the contents are undefined, only + * by acquiring wait_lock there is a guarantee that + * they are not invalid when reading. + * + * As such, when deadlock detection needs to be + * performed the optimistic spinning cannot be done. + */ + if (ACCESS_ONCE(ww->ctx)) + goto slowpath; + } + + /* + * If there's an owner, wait for it to either + * release the lock or go to sleep. + */ + mspin_lock(MLOCK(lock), &node); + owner = ACCESS_ONCE(lock->owner); + if (owner && !mutex_spin_on_owner(lock, owner)) { + mspin_unlock(MLOCK(lock), &node); + goto slowpath; + } + + if ((atomic_read(&lock->count) == 1) && + (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { + lock_acquired(&lock->dep_map, ip); + if (use_ww_ctx) { + struct ww_mutex *ww; + ww = container_of(lock, struct ww_mutex, base); + + ww_mutex_set_context_fastpath(ww, ww_ctx); + } + + mutex_set_owner(lock); + mspin_unlock(MLOCK(lock), &node); + preempt_enable(); + return 0; + } + mspin_unlock(MLOCK(lock), &node); + + /* + * When there's no owner, we might have preempted between the + * owner acquiring the lock and setting the owner field. If + * we're an RT task that will live-lock because we won't let + * the owner complete. + */ + if (!owner && (need_resched() || rt_task(task))) + goto slowpath; + + /* + * The cpu_relax() call is a compiler barrier which forces + * everything in this loop to be re-loaded. We don't need + * memory barriers as we'll eventually observe the right + * values at the cost of a few extra spins. + */ + arch_mutex_cpu_relax(); + } +slowpath: +#endif + spin_lock_mutex(&lock->wait_lock, flags); + + /* once more, can we acquire the lock? */ + if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1)) + goto skip_wait; + + debug_mutex_lock_common(lock, &waiter); + debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); + + /* add waiting tasks to the end of the waitqueue (FIFO): */ + list_add_tail(&waiter.list, &lock->wait_list); + waiter.task = task; + + lock_contended(&lock->dep_map, ip); + + for (;;) { + /* + * Lets try to take the lock again - this is needed even if + * we get here for the first time (shortly after failing to + * acquire the lock), to make sure that we get a wakeup once + * it's unlocked. Later on, if we sleep, this is the + * operation that gives us the lock. We xchg it to -1, so + * that when we release the lock, we properly wake up the + * other waiters: + */ + if (MUTEX_SHOW_NO_WAITER(lock) && + (atomic_xchg(&lock->count, -1) == 1)) + break; + + /* + * got a signal? (This code gets eliminated in the + * TASK_UNINTERRUPTIBLE case.) + */ + if (unlikely(signal_pending_state(state, task))) { + ret = -EINTR; + goto err; + } + + if (use_ww_ctx && ww_ctx->acquired > 0) { + ret = __mutex_lock_check_stamp(lock, ww_ctx); + if (ret) + goto err; + } + + __set_task_state(task, state); + + /* didn't get the lock, go to sleep: */ + spin_unlock_mutex(&lock->wait_lock, flags); + schedule_preempt_disabled(); + spin_lock_mutex(&lock->wait_lock, flags); + } + mutex_remove_waiter(lock, &waiter, current_thread_info()); + /* set it to 0 if there are no waiters left: */ + if (likely(list_empty(&lock->wait_list))) + atomic_set(&lock->count, 0); + debug_mutex_free_waiter(&waiter); + +skip_wait: + /* got the lock - cleanup and rejoice! */ + lock_acquired(&lock->dep_map, ip); + mutex_set_owner(lock); + + if (use_ww_ctx) { + struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); + struct mutex_waiter *cur; + + /* + * This branch gets optimized out for the common case, + * and is only important for ww_mutex_lock. + */ + ww_mutex_lock_acquired(ww, ww_ctx); + ww->ctx = ww_ctx; + + /* + * Give any possible sleeping processes the chance to wake up, + * so they can recheck if they have to back off. + */ + list_for_each_entry(cur, &lock->wait_list, list) { + debug_mutex_wake_waiter(lock, cur); + wake_up_process(cur->task); + } + } + + spin_unlock_mutex(&lock->wait_lock, flags); + preempt_enable(); + return 0; + +err: + mutex_remove_waiter(lock, &waiter, task_thread_info(task)); + spin_unlock_mutex(&lock->wait_lock, flags); + debug_mutex_free_waiter(&waiter); + mutex_release(&lock->dep_map, 1, ip); + preempt_enable(); + return ret; +} + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +void __sched +mutex_lock_nested(struct mutex *lock, unsigned int subclass) +{ + might_sleep(); + __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, + subclass, NULL, _RET_IP_, NULL, 0); +} + +EXPORT_SYMBOL_GPL(mutex_lock_nested); + +void __sched +_mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) +{ + might_sleep(); + __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, + 0, nest, _RET_IP_, NULL, 0); +} + +EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); + +int __sched +mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) +{ + might_sleep(); + return __mutex_lock_common(lock, TASK_KILLABLE, + subclass, NULL, _RET_IP_, NULL, 0); +} +EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); + +int __sched +mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) +{ + might_sleep(); + return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, + subclass, NULL, _RET_IP_, NULL, 0); +} + +EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); + +static inline int +ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) +{ +#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH + unsigned tmp; + + if (ctx->deadlock_inject_countdown-- == 0) { + tmp = ctx->deadlock_inject_interval; + if (tmp > UINT_MAX/4) + tmp = UINT_MAX; + else + tmp = tmp*2 + tmp + tmp/2; + + ctx->deadlock_inject_interval = tmp; + ctx->deadlock_inject_countdown = tmp; + ctx->contending_lock = lock; + + ww_mutex_unlock(lock); + + return -EDEADLK; + } +#endif + + return 0; +} + +int __sched +__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) +{ + int ret; + + might_sleep(); + ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, + 0, &ctx->dep_map, _RET_IP_, ctx, 1); + if (!ret && ctx->acquired > 1) + return ww_mutex_deadlock_injection(lock, ctx); + + return ret; +} +EXPORT_SYMBOL_GPL(__ww_mutex_lock); + +int __sched +__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) +{ + int ret; + + might_sleep(); + ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, + 0, &ctx->dep_map, _RET_IP_, ctx, 1); + + if (!ret && ctx->acquired > 1) + return ww_mutex_deadlock_injection(lock, ctx); + + return ret; +} +EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible); + +#endif + +/* + * Release the lock, slowpath: + */ +static inline void +__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) +{ + struct mutex *lock = container_of(lock_count, struct mutex, count); + unsigned long flags; + + spin_lock_mutex(&lock->wait_lock, flags); + mutex_release(&lock->dep_map, nested, _RET_IP_); + debug_mutex_unlock(lock); + + /* + * some architectures leave the lock unlocked in the fastpath failure + * case, others need to leave it locked. In the later case we have to + * unlock it here + */ + if (__mutex_slowpath_needs_to_unlock()) + atomic_set(&lock->count, 1); + + if (!list_empty(&lock->wait_list)) { + /* get the first entry from the wait-list: */ + struct mutex_waiter *waiter = + list_entry(lock->wait_list.next, + struct mutex_waiter, list); + + debug_mutex_wake_waiter(lock, waiter); + + wake_up_process(waiter->task); + } + + spin_unlock_mutex(&lock->wait_lock, flags); +} + +/* + * Release the lock, slowpath: + */ +static __used noinline void +__mutex_unlock_slowpath(atomic_t *lock_count) +{ + __mutex_unlock_common_slowpath(lock_count, 1); +} + +#ifndef CONFIG_DEBUG_LOCK_ALLOC +/* + * Here come the less common (and hence less performance-critical) APIs: + * mutex_lock_interruptible() and mutex_trylock(). + */ +static noinline int __sched +__mutex_lock_killable_slowpath(struct mutex *lock); + +static noinline int __sched +__mutex_lock_interruptible_slowpath(struct mutex *lock); + +/** + * mutex_lock_interruptible - acquire the mutex, interruptible + * @lock: the mutex to be acquired + * + * Lock the mutex like mutex_lock(), and return 0 if the mutex has + * been acquired or sleep until the mutex becomes available. If a + * signal arrives while waiting for the lock then this function + * returns -EINTR. + * + * This function is similar to (but not equivalent to) down_interruptible(). + */ +int __sched mutex_lock_interruptible(struct mutex *lock) +{ + int ret; + + might_sleep(); + ret = __mutex_fastpath_lock_retval(&lock->count); + if (likely(!ret)) { + mutex_set_owner(lock); + return 0; + } else + return __mutex_lock_interruptible_slowpath(lock); +} + +EXPORT_SYMBOL(mutex_lock_interruptible); + +int __sched mutex_lock_killable(struct mutex *lock) +{ + int ret; + + might_sleep(); + ret = __mutex_fastpath_lock_retval(&lock->count); + if (likely(!ret)) { + mutex_set_owner(lock); + return 0; + } else + return __mutex_lock_killable_slowpath(lock); +} +EXPORT_SYMBOL(mutex_lock_killable); + +static __used noinline void __sched +__mutex_lock_slowpath(atomic_t *lock_count) +{ + struct mutex *lock = container_of(lock_count, struct mutex, count); + + __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, + NULL, _RET_IP_, NULL, 0); +} + +static noinline int __sched +__mutex_lock_killable_slowpath(struct mutex *lock) +{ + return __mutex_lock_common(lock, TASK_KILLABLE, 0, + NULL, _RET_IP_, NULL, 0); +} + +static noinline int __sched +__mutex_lock_interruptible_slowpath(struct mutex *lock) +{ + return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, + NULL, _RET_IP_, NULL, 0); +} + +static noinline int __sched +__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) +{ + return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0, + NULL, _RET_IP_, ctx, 1); +} + +static noinline int __sched +__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, + struct ww_acquire_ctx *ctx) +{ + return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0, + NULL, _RET_IP_, ctx, 1); +} + +#endif + +/* + * Spinlock based trylock, we take the spinlock and check whether we + * can get the lock: + */ +static inline int __mutex_trylock_slowpath(atomic_t *lock_count) +{ + struct mutex *lock = container_of(lock_count, struct mutex, count); + unsigned long flags; + int prev; + + spin_lock_mutex(&lock->wait_lock, flags); + + prev = atomic_xchg(&lock->count, -1); + if (likely(prev == 1)) { + mutex_set_owner(lock); + mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); + } + + /* Set it back to 0 if there are no waiters: */ + if (likely(list_empty(&lock->wait_list))) + atomic_set(&lock->count, 0); + + spin_unlock_mutex(&lock->wait_lock, flags); + + return prev == 1; +} + +/** + * mutex_trylock - try to acquire the mutex, without waiting + * @lock: the mutex to be acquired + * + * Try to acquire the mutex atomically. Returns 1 if the mutex + * has been acquired successfully, and 0 on contention. + * + * NOTE: this function follows the spin_trylock() convention, so + * it is negated from the down_trylock() return values! Be careful + * about this when converting semaphore users to mutexes. + * + * This function must not be used in interrupt context. The + * mutex must be released by the same task that acquired it. + */ +int __sched mutex_trylock(struct mutex *lock) +{ + int ret; + + ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); + if (ret) + mutex_set_owner(lock); + + return ret; +} +EXPORT_SYMBOL(mutex_trylock); + +#ifndef CONFIG_DEBUG_LOCK_ALLOC +int __sched +__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) +{ + int ret; + + might_sleep(); + + ret = __mutex_fastpath_lock_retval(&lock->base.count); + + if (likely(!ret)) { + ww_mutex_set_context_fastpath(lock, ctx); + mutex_set_owner(&lock->base); + } else + ret = __ww_mutex_lock_slowpath(lock, ctx); + return ret; +} +EXPORT_SYMBOL(__ww_mutex_lock); + +int __sched +__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) +{ + int ret; + + might_sleep(); + + ret = __mutex_fastpath_lock_retval(&lock->base.count); + + if (likely(!ret)) { + ww_mutex_set_context_fastpath(lock, ctx); + mutex_set_owner(&lock->base); + } else + ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx); + return ret; +} +EXPORT_SYMBOL(__ww_mutex_lock_interruptible); + +#endif + +/** + * 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); Index: linux-2.6/kernel/locking/mutex.h =================================================================== --- /dev/null +++ linux-2.6/kernel/locking/mutex.h @@ -0,0 +1,48 @@ +/* + * Mutexes: blocking mutual exclusion locks + * + * started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar + * + * This file contains mutex debugging related internal prototypes, for the + * !CONFIG_DEBUG_MUTEXES case. Most of them are NOPs: + */ + +#define spin_lock_mutex(lock, flags) \ + do { spin_lock(lock); (void)(flags); } while (0) +#define spin_unlock_mutex(lock, flags) \ + do { spin_unlock(lock); (void)(flags); } while (0) +#define mutex_remove_waiter(lock, waiter, ti) \ + __list_del((waiter)->list.prev, (waiter)->list.next) + +#ifdef CONFIG_SMP +static inline void mutex_set_owner(struct mutex *lock) +{ + lock->owner = current; +} + +static inline void mutex_clear_owner(struct mutex *lock) +{ + lock->owner = NULL; +} +#else +static inline void mutex_set_owner(struct mutex *lock) +{ +} + +static inline void mutex_clear_owner(struct mutex *lock) +{ +} +#endif + +#define debug_mutex_wake_waiter(lock, waiter) do { } while (0) +#define debug_mutex_free_waiter(waiter) do { } while (0) +#define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0) +#define debug_mutex_unlock(lock) do { } while (0) +#define debug_mutex_init(lock, name, key) do { } while (0) + +static inline void +debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter) +{ +} Index: linux-2.6/kernel/mutex-debug.c =================================================================== --- linux-2.6.orig/kernel/mutex-debug.c +++ /dev/null @@ -1,110 +0,0 @@ -/* - * kernel/mutex-debug.c - * - * Debugging code for mutexes - * - * Started by Ingo Molnar: - * - * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar - * - * lock debugging, locking tree, deadlock detection started by: - * - * Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey - * Released under the General Public License (GPL). - */ -#include -#include -#include -#include -#include -#include -#include -#include -#include - -#include "mutex-debug.h" - -/* - * Must be called with lock->wait_lock held. - */ -void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter) -{ - memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter)); - waiter->magic = waiter; - INIT_LIST_HEAD(&waiter->list); -} - -void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter) -{ - SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock)); - DEBUG_LOCKS_WARN_ON(list_empty(&lock->wait_list)); - DEBUG_LOCKS_WARN_ON(waiter->magic != waiter); - DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list)); -} - -void debug_mutex_free_waiter(struct mutex_waiter *waiter) -{ - DEBUG_LOCKS_WARN_ON(!list_empty(&waiter->list)); - memset(waiter, MUTEX_DEBUG_FREE, sizeof(*waiter)); -} - -void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter, - struct thread_info *ti) -{ - SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock)); - - /* Mark the current thread as blocked on the lock: */ - ti->task->blocked_on = waiter; -} - -void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, - struct thread_info *ti) -{ - DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list)); - DEBUG_LOCKS_WARN_ON(waiter->task != ti->task); - DEBUG_LOCKS_WARN_ON(ti->task->blocked_on != waiter); - ti->task->blocked_on = NULL; - - list_del_init(&waiter->list); - waiter->task = NULL; -} - -void debug_mutex_unlock(struct mutex *lock) -{ - if (unlikely(!debug_locks)) - return; - - DEBUG_LOCKS_WARN_ON(lock->magic != lock); - DEBUG_LOCKS_WARN_ON(lock->owner != current); - DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next); - mutex_clear_owner(lock); -} - -void debug_mutex_init(struct mutex *lock, 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 *)lock, sizeof(*lock)); - lockdep_init_map(&lock->dep_map, name, key, 0); -#endif - lock->magic = lock; -} - -/*** - * mutex_destroy - mark a mutex unusable - * @lock: the mutex to be destroyed - * - * This function marks the mutex uninitialized, and any subsequent - * use of the mutex is forbidden. The mutex must not be locked when - * this function is called. - */ -void mutex_destroy(struct mutex *lock) -{ - DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock)); - lock->magic = NULL; -} - -EXPORT_SYMBOL_GPL(mutex_destroy); Index: linux-2.6/kernel/mutex-debug.h =================================================================== --- linux-2.6.orig/kernel/mutex-debug.h +++ /dev/null @@ -1,55 +0,0 @@ -/* - * Mutexes: blocking mutual exclusion locks - * - * started by Ingo Molnar: - * - * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar - * - * This file contains mutex debugging related internal declarations, - * prototypes and inline functions, for the CONFIG_DEBUG_MUTEXES case. - * More details are in kernel/mutex-debug.c. - */ - -/* - * This must be called with lock->wait_lock held. - */ -extern void debug_mutex_lock_common(struct mutex *lock, - struct mutex_waiter *waiter); -extern void debug_mutex_wake_waiter(struct mutex *lock, - struct mutex_waiter *waiter); -extern void debug_mutex_free_waiter(struct mutex_waiter *waiter); -extern void debug_mutex_add_waiter(struct mutex *lock, - struct mutex_waiter *waiter, - struct thread_info *ti); -extern void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, - struct thread_info *ti); -extern void debug_mutex_unlock(struct mutex *lock); -extern void debug_mutex_init(struct mutex *lock, const char *name, - struct lock_class_key *key); - -static inline void mutex_set_owner(struct mutex *lock) -{ - lock->owner = current; -} - -static inline void mutex_clear_owner(struct mutex *lock) -{ - lock->owner = NULL; -} - -#define spin_lock_mutex(lock, flags) \ - do { \ - struct mutex *l = container_of(lock, struct mutex, wait_lock); \ - \ - DEBUG_LOCKS_WARN_ON(in_interrupt()); \ - local_irq_save(flags); \ - arch_spin_lock(&(lock)->rlock.raw_lock);\ - DEBUG_LOCKS_WARN_ON(l->magic != l); \ - } while (0) - -#define spin_unlock_mutex(lock, flags) \ - do { \ - arch_spin_unlock(&(lock)->rlock.raw_lock); \ - local_irq_restore(flags); \ - preempt_check_resched(); \ - } while (0) Index: linux-2.6/kernel/mutex.c =================================================================== --- linux-2.6.orig/kernel/mutex.c +++ /dev/null @@ -1,960 +0,0 @@ -/* - * kernel/mutex.c - * - * Mutexes: blocking mutual exclusion locks - * - * Started by Ingo Molnar: - * - * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar - * - * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and - * David Howells for suggestions and improvements. - * - * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline - * from the -rt tree, where it was originally implemented for rtmutexes - * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale - * and Sven Dietrich. - * - * Also see Documentation/mutex-design.txt. - */ -#include -#include -#include -#include -#include -#include -#include -#include - -/* - * In the DEBUG case we are using the "NULL fastpath" for mutexes, - * which forces all calls into the slowpath: - */ -#ifdef CONFIG_DEBUG_MUTEXES -# include "mutex-debug.h" -# include -#else -# include "mutex.h" -# include -#endif - -/* - * A negative mutex count indicates that waiters are sleeping waiting for the - * mutex. - */ -#define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) - -void -__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) -{ - atomic_set(&lock->count, 1); - spin_lock_init(&lock->wait_lock); - INIT_LIST_HEAD(&lock->wait_list); - mutex_clear_owner(lock); -#ifdef CONFIG_MUTEX_SPIN_ON_OWNER - lock->spin_mlock = NULL; -#endif - - debug_mutex_init(lock, name, key); -} - -EXPORT_SYMBOL(__mutex_init); - -#ifndef CONFIG_DEBUG_LOCK_ALLOC -/* - * We split the mutex lock/unlock logic into separate fastpath and - * slowpath functions, to reduce the register pressure on the fastpath. - * We also put the fastpath first in the kernel image, to make sure the - * branch is predicted by the CPU as default-untaken. - */ -static __used noinline void __sched -__mutex_lock_slowpath(atomic_t *lock_count); - -/** - * mutex_lock - acquire the mutex - * @lock: the mutex to be acquired - * - * Lock the mutex exclusively for this task. If the mutex is not - * available right now, it will sleep until it can get it. - * - * The mutex must later on be released by the same task that - * acquired it. Recursive locking is not allowed. The task - * may not exit without first unlocking the mutex. Also, kernel - * memory where the mutex resides mutex must not be freed with - * the mutex still locked. The mutex must first be initialized - * (or statically defined) before it can be locked. memset()-ing - * the mutex to 0 is not allowed. - * - * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging - * checks that will enforce the restrictions and will also do - * deadlock debugging. ) - * - * This function is similar to (but not equivalent to) down(). - */ -void __sched mutex_lock(struct mutex *lock) -{ - might_sleep(); - /* - * The locking fastpath is the 1->0 transition from - * 'unlocked' into 'locked' state. - */ - __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); - mutex_set_owner(lock); -} - -EXPORT_SYMBOL(mutex_lock); -#endif - -#ifdef CONFIG_MUTEX_SPIN_ON_OWNER -/* - * In order to avoid a stampede of mutex spinners from acquiring the mutex - * more or less simultaneously, the spinners need to acquire a MCS lock - * first before spinning on the owner field. - * - * We don't inline mspin_lock() so that perf can correctly account for the - * time spent in this lock function. - */ -struct mspin_node { - struct mspin_node *next ; - int locked; /* 1 if lock acquired */ -}; -#define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock)) - -static noinline -void mspin_lock(struct mspin_node **lock, struct mspin_node *node) -{ - struct mspin_node *prev; - - /* Init node */ - node->locked = 0; - node->next = NULL; - - prev = xchg(lock, node); - if (likely(prev == NULL)) { - /* Lock acquired */ - node->locked = 1; - return; - } - ACCESS_ONCE(prev->next) = node; - smp_wmb(); - /* Wait until the lock holder passes the lock down */ - while (!ACCESS_ONCE(node->locked)) - arch_mutex_cpu_relax(); -} - -static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node) -{ - struct mspin_node *next = ACCESS_ONCE(node->next); - - if (likely(!next)) { - /* - * Release the lock by setting it to NULL - */ - if (cmpxchg(lock, node, NULL) == node) - return; - /* Wait until the next pointer is set */ - while (!(next = ACCESS_ONCE(node->next))) - arch_mutex_cpu_relax(); - } - ACCESS_ONCE(next->locked) = 1; - smp_wmb(); -} - -/* - * Mutex spinning code migrated from kernel/sched/core.c - */ - -static inline bool owner_running(struct mutex *lock, struct task_struct *owner) -{ - if (lock->owner != owner) - return false; - - /* - * Ensure we emit the owner->on_cpu, dereference _after_ checking - * lock->owner still matches owner, if that fails, owner might - * point to free()d memory, if it still matches, the rcu_read_lock() - * ensures the memory stays valid. - */ - barrier(); - - return owner->on_cpu; -} - -/* - * Look out! "owner" is an entirely speculative pointer - * access and not reliable. - */ -static noinline -int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) -{ - rcu_read_lock(); - while (owner_running(lock, owner)) { - if (need_resched()) - break; - - arch_mutex_cpu_relax(); - } - rcu_read_unlock(); - - /* - * We break out the loop above on need_resched() and when the - * owner changed, which is a sign for heavy contention. Return - * success only when lock->owner is NULL. - */ - return lock->owner == NULL; -} - -/* - * Initial check for entering the mutex spinning loop - */ -static inline int mutex_can_spin_on_owner(struct mutex *lock) -{ - struct task_struct *owner; - int retval = 1; - - rcu_read_lock(); - owner = ACCESS_ONCE(lock->owner); - if (owner) - retval = owner->on_cpu; - rcu_read_unlock(); - /* - * if lock->owner is not set, the mutex owner may have just acquired - * it and not set the owner yet or the mutex has been released. - */ - return retval; -} -#endif - -static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count); - -/** - * mutex_unlock - release the mutex - * @lock: the mutex to be released - * - * Unlock a mutex that has been locked by this task previously. - * - * This function must not be used in interrupt context. Unlocking - * of a not locked mutex is not allowed. - * - * This function is similar to (but not equivalent to) up(). - */ -void __sched mutex_unlock(struct mutex *lock) -{ - /* - * The unlocking fastpath is the 0->1 transition from 'locked' - * into 'unlocked' state: - */ -#ifndef CONFIG_DEBUG_MUTEXES - /* - * When debugging is enabled we must not clear the owner before time, - * the slow path will always be taken, and that clears the owner field - * after verifying that it was indeed current. - */ - mutex_clear_owner(lock); -#endif - __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); -} - -EXPORT_SYMBOL(mutex_unlock); - -/** - * ww_mutex_unlock - release the w/w mutex - * @lock: the mutex to be released - * - * Unlock a mutex that has been locked by this task previously with any of the - * ww_mutex_lock* functions (with or without an acquire context). It is - * forbidden to release the locks after releasing the acquire context. - * - * This function must not be used in interrupt context. Unlocking - * of a unlocked mutex is not allowed. - */ -void __sched ww_mutex_unlock(struct ww_mutex *lock) -{ - /* - * The unlocking fastpath is the 0->1 transition from 'locked' - * into 'unlocked' state: - */ - if (lock->ctx) { -#ifdef CONFIG_DEBUG_MUTEXES - DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); -#endif - if (lock->ctx->acquired > 0) - lock->ctx->acquired--; - lock->ctx = NULL; - } - -#ifndef CONFIG_DEBUG_MUTEXES - /* - * When debugging is enabled we must not clear the owner before time, - * the slow path will always be taken, and that clears the owner field - * after verifying that it was indeed current. - */ - mutex_clear_owner(&lock->base); -#endif - __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath); -} -EXPORT_SYMBOL(ww_mutex_unlock); - -static inline int __sched -__mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx) -{ - struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); - struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx); - - if (!hold_ctx) - return 0; - - if (unlikely(ctx == hold_ctx)) - return -EALREADY; - - if (ctx->stamp - hold_ctx->stamp <= LONG_MAX && - (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) { -#ifdef CONFIG_DEBUG_MUTEXES - DEBUG_LOCKS_WARN_ON(ctx->contending_lock); - ctx->contending_lock = ww; -#endif - return -EDEADLK; - } - - return 0; -} - -static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww, - struct ww_acquire_ctx *ww_ctx) -{ -#ifdef CONFIG_DEBUG_MUTEXES - /* - * If this WARN_ON triggers, you used ww_mutex_lock to acquire, - * but released with a normal mutex_unlock in this call. - * - * This should never happen, always use ww_mutex_unlock. - */ - DEBUG_LOCKS_WARN_ON(ww->ctx); - - /* - * Not quite done after calling ww_acquire_done() ? - */ - DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); - - if (ww_ctx->contending_lock) { - /* - * After -EDEADLK you tried to - * acquire a different ww_mutex? Bad! - */ - DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); - - /* - * You called ww_mutex_lock after receiving -EDEADLK, - * but 'forgot' to unlock everything else first? - */ - DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); - ww_ctx->contending_lock = NULL; - } - - /* - * Naughty, using a different class will lead to undefined behavior! - */ - DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); -#endif - ww_ctx->acquired++; -} - -/* - * after acquiring lock with fastpath or when we lost out in contested - * slowpath, set ctx and wake up any waiters so they can recheck. - * - * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set, - * as the fastpath and opportunistic spinning are disabled in that case. - */ -static __always_inline void -ww_mutex_set_context_fastpath(struct ww_mutex *lock, - struct ww_acquire_ctx *ctx) -{ - unsigned long flags; - struct mutex_waiter *cur; - - ww_mutex_lock_acquired(lock, ctx); - - lock->ctx = ctx; - - /* - * The lock->ctx update should be visible on all cores before - * the atomic read is done, otherwise contended waiters might be - * missed. The contended waiters will either see ww_ctx == NULL - * and keep spinning, or it will acquire wait_lock, add itself - * to waiter list and sleep. - */ - smp_mb(); /* ^^^ */ - - /* - * Check if lock is contended, if not there is nobody to wake up - */ - if (likely(atomic_read(&lock->base.count) == 0)) - return; - - /* - * Uh oh, we raced in fastpath, wake up everyone in this case, - * so they can see the new lock->ctx. - */ - spin_lock_mutex(&lock->base.wait_lock, flags); - list_for_each_entry(cur, &lock->base.wait_list, list) { - debug_mutex_wake_waiter(&lock->base, cur); - wake_up_process(cur->task); - } - spin_unlock_mutex(&lock->base.wait_lock, flags); -} - -/* - * Lock a mutex (possibly interruptible), slowpath: - */ -static __always_inline int __sched -__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, - struct lockdep_map *nest_lock, unsigned long ip, - struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) -{ - struct task_struct *task = current; - struct mutex_waiter waiter; - unsigned long flags; - int ret; - - preempt_disable(); - mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); - -#ifdef CONFIG_MUTEX_SPIN_ON_OWNER - /* - * Optimistic spinning. - * - * We try to spin for acquisition when we find that there are no - * pending waiters and the lock owner is currently running on a - * (different) CPU. - * - * The rationale is that if the lock owner is running, it is likely to - * release the lock soon. - * - * Since this needs the lock owner, and this mutex implementation - * doesn't track the owner atomically in the lock field, we need to - * track it non-atomically. - * - * We can't do this for DEBUG_MUTEXES because that relies on wait_lock - * to serialize everything. - * - * The mutex spinners are queued up using MCS lock so that only one - * spinner can compete for the mutex. However, if mutex spinning isn't - * going to happen, there is no point in going through the lock/unlock - * overhead. - */ - if (!mutex_can_spin_on_owner(lock)) - goto slowpath; - - for (;;) { - struct task_struct *owner; - struct mspin_node node; - - if (use_ww_ctx && ww_ctx->acquired > 0) { - struct ww_mutex *ww; - - ww = container_of(lock, struct ww_mutex, base); - /* - * If ww->ctx is set the contents are undefined, only - * by acquiring wait_lock there is a guarantee that - * they are not invalid when reading. - * - * As such, when deadlock detection needs to be - * performed the optimistic spinning cannot be done. - */ - if (ACCESS_ONCE(ww->ctx)) - goto slowpath; - } - - /* - * If there's an owner, wait for it to either - * release the lock or go to sleep. - */ - mspin_lock(MLOCK(lock), &node); - owner = ACCESS_ONCE(lock->owner); - if (owner && !mutex_spin_on_owner(lock, owner)) { - mspin_unlock(MLOCK(lock), &node); - goto slowpath; - } - - if ((atomic_read(&lock->count) == 1) && - (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { - lock_acquired(&lock->dep_map, ip); - if (use_ww_ctx) { - struct ww_mutex *ww; - ww = container_of(lock, struct ww_mutex, base); - - ww_mutex_set_context_fastpath(ww, ww_ctx); - } - - mutex_set_owner(lock); - mspin_unlock(MLOCK(lock), &node); - preempt_enable(); - return 0; - } - mspin_unlock(MLOCK(lock), &node); - - /* - * When there's no owner, we might have preempted between the - * owner acquiring the lock and setting the owner field. If - * we're an RT task that will live-lock because we won't let - * the owner complete. - */ - if (!owner && (need_resched() || rt_task(task))) - goto slowpath; - - /* - * The cpu_relax() call is a compiler barrier which forces - * everything in this loop to be re-loaded. We don't need - * memory barriers as we'll eventually observe the right - * values at the cost of a few extra spins. - */ - arch_mutex_cpu_relax(); - } -slowpath: -#endif - spin_lock_mutex(&lock->wait_lock, flags); - - /* once more, can we acquire the lock? */ - if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1)) - goto skip_wait; - - debug_mutex_lock_common(lock, &waiter); - debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); - - /* add waiting tasks to the end of the waitqueue (FIFO): */ - list_add_tail(&waiter.list, &lock->wait_list); - waiter.task = task; - - lock_contended(&lock->dep_map, ip); - - for (;;) { - /* - * Lets try to take the lock again - this is needed even if - * we get here for the first time (shortly after failing to - * acquire the lock), to make sure that we get a wakeup once - * it's unlocked. Later on, if we sleep, this is the - * operation that gives us the lock. We xchg it to -1, so - * that when we release the lock, we properly wake up the - * other waiters: - */ - if (MUTEX_SHOW_NO_WAITER(lock) && - (atomic_xchg(&lock->count, -1) == 1)) - break; - - /* - * got a signal? (This code gets eliminated in the - * TASK_UNINTERRUPTIBLE case.) - */ - if (unlikely(signal_pending_state(state, task))) { - ret = -EINTR; - goto err; - } - - if (use_ww_ctx && ww_ctx->acquired > 0) { - ret = __mutex_lock_check_stamp(lock, ww_ctx); - if (ret) - goto err; - } - - __set_task_state(task, state); - - /* didn't get the lock, go to sleep: */ - spin_unlock_mutex(&lock->wait_lock, flags); - schedule_preempt_disabled(); - spin_lock_mutex(&lock->wait_lock, flags); - } - mutex_remove_waiter(lock, &waiter, current_thread_info()); - /* set it to 0 if there are no waiters left: */ - if (likely(list_empty(&lock->wait_list))) - atomic_set(&lock->count, 0); - debug_mutex_free_waiter(&waiter); - -skip_wait: - /* got the lock - cleanup and rejoice! */ - lock_acquired(&lock->dep_map, ip); - mutex_set_owner(lock); - - if (use_ww_ctx) { - struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); - struct mutex_waiter *cur; - - /* - * This branch gets optimized out for the common case, - * and is only important for ww_mutex_lock. - */ - ww_mutex_lock_acquired(ww, ww_ctx); - ww->ctx = ww_ctx; - - /* - * Give any possible sleeping processes the chance to wake up, - * so they can recheck if they have to back off. - */ - list_for_each_entry(cur, &lock->wait_list, list) { - debug_mutex_wake_waiter(lock, cur); - wake_up_process(cur->task); - } - } - - spin_unlock_mutex(&lock->wait_lock, flags); - preempt_enable(); - return 0; - -err: - mutex_remove_waiter(lock, &waiter, task_thread_info(task)); - spin_unlock_mutex(&lock->wait_lock, flags); - debug_mutex_free_waiter(&waiter); - mutex_release(&lock->dep_map, 1, ip); - preempt_enable(); - return ret; -} - -#ifdef CONFIG_DEBUG_LOCK_ALLOC -void __sched -mutex_lock_nested(struct mutex *lock, unsigned int subclass) -{ - might_sleep(); - __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, - subclass, NULL, _RET_IP_, NULL, 0); -} - -EXPORT_SYMBOL_GPL(mutex_lock_nested); - -void __sched -_mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) -{ - might_sleep(); - __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, - 0, nest, _RET_IP_, NULL, 0); -} - -EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); - -int __sched -mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) -{ - might_sleep(); - return __mutex_lock_common(lock, TASK_KILLABLE, - subclass, NULL, _RET_IP_, NULL, 0); -} -EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); - -int __sched -mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) -{ - might_sleep(); - return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, - subclass, NULL, _RET_IP_, NULL, 0); -} - -EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); - -static inline int -ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) -{ -#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH - unsigned tmp; - - if (ctx->deadlock_inject_countdown-- == 0) { - tmp = ctx->deadlock_inject_interval; - if (tmp > UINT_MAX/4) - tmp = UINT_MAX; - else - tmp = tmp*2 + tmp + tmp/2; - - ctx->deadlock_inject_interval = tmp; - ctx->deadlock_inject_countdown = tmp; - ctx->contending_lock = lock; - - ww_mutex_unlock(lock); - - return -EDEADLK; - } -#endif - - return 0; -} - -int __sched -__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) -{ - int ret; - - might_sleep(); - ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, - 0, &ctx->dep_map, _RET_IP_, ctx, 1); - if (!ret && ctx->acquired > 1) - return ww_mutex_deadlock_injection(lock, ctx); - - return ret; -} -EXPORT_SYMBOL_GPL(__ww_mutex_lock); - -int __sched -__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) -{ - int ret; - - might_sleep(); - ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, - 0, &ctx->dep_map, _RET_IP_, ctx, 1); - - if (!ret && ctx->acquired > 1) - return ww_mutex_deadlock_injection(lock, ctx); - - return ret; -} -EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible); - -#endif - -/* - * Release the lock, slowpath: - */ -static inline void -__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) -{ - struct mutex *lock = container_of(lock_count, struct mutex, count); - unsigned long flags; - - spin_lock_mutex(&lock->wait_lock, flags); - mutex_release(&lock->dep_map, nested, _RET_IP_); - debug_mutex_unlock(lock); - - /* - * some architectures leave the lock unlocked in the fastpath failure - * case, others need to leave it locked. In the later case we have to - * unlock it here - */ - if (__mutex_slowpath_needs_to_unlock()) - atomic_set(&lock->count, 1); - - if (!list_empty(&lock->wait_list)) { - /* get the first entry from the wait-list: */ - struct mutex_waiter *waiter = - list_entry(lock->wait_list.next, - struct mutex_waiter, list); - - debug_mutex_wake_waiter(lock, waiter); - - wake_up_process(waiter->task); - } - - spin_unlock_mutex(&lock->wait_lock, flags); -} - -/* - * Release the lock, slowpath: - */ -static __used noinline void -__mutex_unlock_slowpath(atomic_t *lock_count) -{ - __mutex_unlock_common_slowpath(lock_count, 1); -} - -#ifndef CONFIG_DEBUG_LOCK_ALLOC -/* - * Here come the less common (and hence less performance-critical) APIs: - * mutex_lock_interruptible() and mutex_trylock(). - */ -static noinline int __sched -__mutex_lock_killable_slowpath(struct mutex *lock); - -static noinline int __sched -__mutex_lock_interruptible_slowpath(struct mutex *lock); - -/** - * mutex_lock_interruptible - acquire the mutex, interruptible - * @lock: the mutex to be acquired - * - * Lock the mutex like mutex_lock(), and return 0 if the mutex has - * been acquired or sleep until the mutex becomes available. If a - * signal arrives while waiting for the lock then this function - * returns -EINTR. - * - * This function is similar to (but not equivalent to) down_interruptible(). - */ -int __sched mutex_lock_interruptible(struct mutex *lock) -{ - int ret; - - might_sleep(); - ret = __mutex_fastpath_lock_retval(&lock->count); - if (likely(!ret)) { - mutex_set_owner(lock); - return 0; - } else - return __mutex_lock_interruptible_slowpath(lock); -} - -EXPORT_SYMBOL(mutex_lock_interruptible); - -int __sched mutex_lock_killable(struct mutex *lock) -{ - int ret; - - might_sleep(); - ret = __mutex_fastpath_lock_retval(&lock->count); - if (likely(!ret)) { - mutex_set_owner(lock); - return 0; - } else - return __mutex_lock_killable_slowpath(lock); -} -EXPORT_SYMBOL(mutex_lock_killable); - -static __used noinline void __sched -__mutex_lock_slowpath(atomic_t *lock_count) -{ - struct mutex *lock = container_of(lock_count, struct mutex, count); - - __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, - NULL, _RET_IP_, NULL, 0); -} - -static noinline int __sched -__mutex_lock_killable_slowpath(struct mutex *lock) -{ - return __mutex_lock_common(lock, TASK_KILLABLE, 0, - NULL, _RET_IP_, NULL, 0); -} - -static noinline int __sched -__mutex_lock_interruptible_slowpath(struct mutex *lock) -{ - return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, - NULL, _RET_IP_, NULL, 0); -} - -static noinline int __sched -__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) -{ - return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0, - NULL, _RET_IP_, ctx, 1); -} - -static noinline int __sched -__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, - struct ww_acquire_ctx *ctx) -{ - return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0, - NULL, _RET_IP_, ctx, 1); -} - -#endif - -/* - * Spinlock based trylock, we take the spinlock and check whether we - * can get the lock: - */ -static inline int __mutex_trylock_slowpath(atomic_t *lock_count) -{ - struct mutex *lock = container_of(lock_count, struct mutex, count); - unsigned long flags; - int prev; - - spin_lock_mutex(&lock->wait_lock, flags); - - prev = atomic_xchg(&lock->count, -1); - if (likely(prev == 1)) { - mutex_set_owner(lock); - mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); - } - - /* Set it back to 0 if there are no waiters: */ - if (likely(list_empty(&lock->wait_list))) - atomic_set(&lock->count, 0); - - spin_unlock_mutex(&lock->wait_lock, flags); - - return prev == 1; -} - -/** - * mutex_trylock - try to acquire the mutex, without waiting - * @lock: the mutex to be acquired - * - * Try to acquire the mutex atomically. Returns 1 if the mutex - * has been acquired successfully, and 0 on contention. - * - * NOTE: this function follows the spin_trylock() convention, so - * it is negated from the down_trylock() return values! Be careful - * about this when converting semaphore users to mutexes. - * - * This function must not be used in interrupt context. The - * mutex must be released by the same task that acquired it. - */ -int __sched mutex_trylock(struct mutex *lock) -{ - int ret; - - ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); - if (ret) - mutex_set_owner(lock); - - return ret; -} -EXPORT_SYMBOL(mutex_trylock); - -#ifndef CONFIG_DEBUG_LOCK_ALLOC -int __sched -__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) -{ - int ret; - - might_sleep(); - - ret = __mutex_fastpath_lock_retval(&lock->base.count); - - if (likely(!ret)) { - ww_mutex_set_context_fastpath(lock, ctx); - mutex_set_owner(&lock->base); - } else - ret = __ww_mutex_lock_slowpath(lock, ctx); - return ret; -} -EXPORT_SYMBOL(__ww_mutex_lock); - -int __sched -__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) -{ - int ret; - - might_sleep(); - - ret = __mutex_fastpath_lock_retval(&lock->base.count); - - if (likely(!ret)) { - ww_mutex_set_context_fastpath(lock, ctx); - mutex_set_owner(&lock->base); - } else - ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx); - return ret; -} -EXPORT_SYMBOL(__ww_mutex_lock_interruptible); - -#endif - -/** - * 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); Index: linux-2.6/kernel/mutex.h =================================================================== --- linux-2.6.orig/kernel/mutex.h +++ /dev/null @@ -1,48 +0,0 @@ -/* - * Mutexes: blocking mutual exclusion locks - * - * started by Ingo Molnar: - * - * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar - * - * This file contains mutex debugging related internal prototypes, for the - * !CONFIG_DEBUG_MUTEXES case. Most of them are NOPs: - */ - -#define spin_lock_mutex(lock, flags) \ - do { spin_lock(lock); (void)(flags); } while (0) -#define spin_unlock_mutex(lock, flags) \ - do { spin_unlock(lock); (void)(flags); } while (0) -#define mutex_remove_waiter(lock, waiter, ti) \ - __list_del((waiter)->list.prev, (waiter)->list.next) - -#ifdef CONFIG_SMP -static inline void mutex_set_owner(struct mutex *lock) -{ - lock->owner = current; -} - -static inline void mutex_clear_owner(struct mutex *lock) -{ - lock->owner = NULL; -} -#else -static inline void mutex_set_owner(struct mutex *lock) -{ -} - -static inline void mutex_clear_owner(struct mutex *lock) -{ -} -#endif - -#define debug_mutex_wake_waiter(lock, waiter) do { } while (0) -#define debug_mutex_free_waiter(waiter) do { } while (0) -#define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0) -#define debug_mutex_unlock(lock) do { } while (0) -#define debug_mutex_init(lock, name, key) do { } while (0) - -static inline void -debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter) -{ -} -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/