From e25a64c4017e3a3cda17454b040737e410a12991 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 31 Oct 2013 18:16:43 +0100 Subject: locking: Move the semaphore core to kernel/locking/ Suggested-by: Ingo Molnar Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-vmw5sf6vzmua1z6nx1cg69h2@git.kernel.org Signed-off-by: Ingo Molnar diff --git a/kernel/Makefile b/kernel/Makefile index 4bce165..45e5ae2 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -8,7 +8,7 @@ obj-y = fork.o exec_domain.o panic.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 \ - hrtimer.o rwsem.o nsproxy.o semaphore.o \ + hrtimer.o rwsem.o nsproxy.o \ notifier.o ksysfs.o cred.o reboot.o \ async.o range.o groups.o lglock.o smpboot.o diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile index 674d215..5978fdd 100644 --- a/kernel/locking/Makefile +++ b/kernel/locking/Makefile @@ -1,5 +1,5 @@ -obj-y += mutex.o +obj-y += mutex.o semaphore.o ifdef CONFIG_FUNCTION_TRACER CFLAGS_REMOVE_lockdep.o = -pg diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c new file mode 100644 index 0000000..6815171 --- /dev/null +++ b/kernel/locking/semaphore.c @@ -0,0 +1,263 @@ +/* + * Copyright (c) 2008 Intel Corporation + * Author: Matthew Wilcox + * + * Distributed under the terms of the GNU GPL, version 2 + * + * This file implements counting semaphores. + * A counting semaphore may be acquired 'n' times before sleeping. + * See mutex.c for single-acquisition sleeping locks which enforce + * rules which allow code to be debugged more easily. + */ + +/* + * Some notes on the implementation: + * + * The spinlock controls access to the other members of the semaphore. + * down_trylock() and up() can be called from interrupt context, so we + * have to disable interrupts when taking the lock. It turns out various + * parts of the kernel expect to be able to use down() on a semaphore in + * interrupt context when they know it will succeed, so we have to use + * irqsave variants for down(), down_interruptible() and down_killable() + * too. + * + * The ->count variable represents how many more tasks can acquire this + * semaphore. If it's zero, there may be tasks waiting on the wait_list. + */ + +#include +#include +#include +#include +#include +#include +#include + +static noinline void __down(struct semaphore *sem); +static noinline int __down_interruptible(struct semaphore *sem); +static noinline int __down_killable(struct semaphore *sem); +static noinline int __down_timeout(struct semaphore *sem, long jiffies); +static noinline void __up(struct semaphore *sem); + +/** + * down - acquire the semaphore + * @sem: the semaphore to be acquired + * + * Acquires the semaphore. If no more tasks are allowed to acquire the + * semaphore, calling this function will put the task to sleep until the + * semaphore is released. + * + * Use of this function is deprecated, please use down_interruptible() or + * down_killable() instead. + */ +void down(struct semaphore *sem) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&sem->lock, flags); + if (likely(sem->count > 0)) + sem->count--; + else + __down(sem); + raw_spin_unlock_irqrestore(&sem->lock, flags); +} +EXPORT_SYMBOL(down); + +/** + * down_interruptible - acquire the semaphore unless interrupted + * @sem: the semaphore to be acquired + * + * Attempts to acquire the semaphore. If no more tasks are allowed to + * acquire the semaphore, calling this function will put the task to sleep. + * If the sleep is interrupted by a signal, this function will return -EINTR. + * If the semaphore is successfully acquired, this function returns 0. + */ +int down_interruptible(struct semaphore *sem) +{ + unsigned long flags; + int result = 0; + + raw_spin_lock_irqsave(&sem->lock, flags); + if (likely(sem->count > 0)) + sem->count--; + else + result = __down_interruptible(sem); + raw_spin_unlock_irqrestore(&sem->lock, flags); + + return result; +} +EXPORT_SYMBOL(down_interruptible); + +/** + * down_killable - acquire the semaphore unless killed + * @sem: the semaphore to be acquired + * + * Attempts to acquire the semaphore. If no more tasks are allowed to + * acquire the semaphore, calling this function will put the task to sleep. + * If the sleep is interrupted by a fatal signal, this function will return + * -EINTR. If the semaphore is successfully acquired, this function returns + * 0. + */ +int down_killable(struct semaphore *sem) +{ + unsigned long flags; + int result = 0; + + raw_spin_lock_irqsave(&sem->lock, flags); + if (likely(sem->count > 0)) + sem->count--; + else + result = __down_killable(sem); + raw_spin_unlock_irqrestore(&sem->lock, flags); + + return result; +} +EXPORT_SYMBOL(down_killable); + +/** + * down_trylock - try to acquire the semaphore, without waiting + * @sem: the semaphore to be acquired + * + * Try to acquire the semaphore atomically. Returns 0 if the semaphore has + * been acquired successfully or 1 if it it cannot be acquired. + * + * NOTE: This return value is inverted from both spin_trylock and + * mutex_trylock! Be careful about this when converting code. + * + * Unlike mutex_trylock, this function can be used from interrupt context, + * and the semaphore can be released by any task or interrupt. + */ +int down_trylock(struct semaphore *sem) +{ + unsigned long flags; + int count; + + raw_spin_lock_irqsave(&sem->lock, flags); + count = sem->count - 1; + if (likely(count >= 0)) + sem->count = count; + raw_spin_unlock_irqrestore(&sem->lock, flags); + + return (count < 0); +} +EXPORT_SYMBOL(down_trylock); + +/** + * down_timeout - acquire the semaphore within a specified time + * @sem: the semaphore to be acquired + * @jiffies: how long to wait before failing + * + * Attempts to acquire the semaphore. If no more tasks are allowed to + * acquire the semaphore, calling this function will put the task to sleep. + * If the semaphore is not released within the specified number of jiffies, + * this function returns -ETIME. It returns 0 if the semaphore was acquired. + */ +int down_timeout(struct semaphore *sem, long jiffies) +{ + unsigned long flags; + int result = 0; + + raw_spin_lock_irqsave(&sem->lock, flags); + if (likely(sem->count > 0)) + sem->count--; + else + result = __down_timeout(sem, jiffies); + raw_spin_unlock_irqrestore(&sem->lock, flags); + + return result; +} +EXPORT_SYMBOL(down_timeout); + +/** + * up - release the semaphore + * @sem: the semaphore to release + * + * Release the semaphore. Unlike mutexes, up() may be called from any + * context and even by tasks which have never called down(). + */ +void up(struct semaphore *sem) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&sem->lock, flags); + if (likely(list_empty(&sem->wait_list))) + sem->count++; + else + __up(sem); + raw_spin_unlock_irqrestore(&sem->lock, flags); +} +EXPORT_SYMBOL(up); + +/* Functions for the contended case */ + +struct semaphore_waiter { + struct list_head list; + struct task_struct *task; + bool up; +}; + +/* + * Because this function is inlined, the 'state' parameter will be + * constant, and thus optimised away by the compiler. Likewise the + * 'timeout' parameter for the cases without timeouts. + */ +static inline int __sched __down_common(struct semaphore *sem, long state, + long timeout) +{ + struct task_struct *task = current; + struct semaphore_waiter waiter; + + list_add_tail(&waiter.list, &sem->wait_list); + waiter.task = task; + waiter.up = false; + + for (;;) { + if (signal_pending_state(state, task)) + goto interrupted; + if (unlikely(timeout <= 0)) + goto timed_out; + __set_task_state(task, state); + raw_spin_unlock_irq(&sem->lock); + timeout = schedule_timeout(timeout); + raw_spin_lock_irq(&sem->lock); + if (waiter.up) + return 0; + } + + timed_out: + list_del(&waiter.list); + return -ETIME; + + interrupted: + list_del(&waiter.list); + return -EINTR; +} + +static noinline void __sched __down(struct semaphore *sem) +{ + __down_common(sem, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); +} + +static noinline int __sched __down_interruptible(struct semaphore *sem) +{ + return __down_common(sem, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); +} + +static noinline int __sched __down_killable(struct semaphore *sem) +{ + return __down_common(sem, TASK_KILLABLE, MAX_SCHEDULE_TIMEOUT); +} + +static noinline int __sched __down_timeout(struct semaphore *sem, long jiffies) +{ + return __down_common(sem, TASK_UNINTERRUPTIBLE, jiffies); +} + +static noinline void __sched __up(struct semaphore *sem) +{ + struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list, + struct semaphore_waiter, list); + list_del(&waiter->list); + waiter->up = true; + wake_up_process(waiter->task); +} diff --git a/kernel/semaphore.c b/kernel/semaphore.c deleted file mode 100644 index 6815171..0000000 --- a/kernel/semaphore.c +++ /dev/null @@ -1,263 +0,0 @@ -/* - * Copyright (c) 2008 Intel Corporation - * Author: Matthew Wilcox - * - * Distributed under the terms of the GNU GPL, version 2 - * - * This file implements counting semaphores. - * A counting semaphore may be acquired 'n' times before sleeping. - * See mutex.c for single-acquisition sleeping locks which enforce - * rules which allow code to be debugged more easily. - */ - -/* - * Some notes on the implementation: - * - * The spinlock controls access to the other members of the semaphore. - * down_trylock() and up() can be called from interrupt context, so we - * have to disable interrupts when taking the lock. It turns out various - * parts of the kernel expect to be able to use down() on a semaphore in - * interrupt context when they know it will succeed, so we have to use - * irqsave variants for down(), down_interruptible() and down_killable() - * too. - * - * The ->count variable represents how many more tasks can acquire this - * semaphore. If it's zero, there may be tasks waiting on the wait_list. - */ - -#include -#include -#include -#include -#include -#include -#include - -static noinline void __down(struct semaphore *sem); -static noinline int __down_interruptible(struct semaphore *sem); -static noinline int __down_killable(struct semaphore *sem); -static noinline int __down_timeout(struct semaphore *sem, long jiffies); -static noinline void __up(struct semaphore *sem); - -/** - * down - acquire the semaphore - * @sem: the semaphore to be acquired - * - * Acquires the semaphore. If no more tasks are allowed to acquire the - * semaphore, calling this function will put the task to sleep until the - * semaphore is released. - * - * Use of this function is deprecated, please use down_interruptible() or - * down_killable() instead. - */ -void down(struct semaphore *sem) -{ - unsigned long flags; - - raw_spin_lock_irqsave(&sem->lock, flags); - if (likely(sem->count > 0)) - sem->count--; - else - __down(sem); - raw_spin_unlock_irqrestore(&sem->lock, flags); -} -EXPORT_SYMBOL(down); - -/** - * down_interruptible - acquire the semaphore unless interrupted - * @sem: the semaphore to be acquired - * - * Attempts to acquire the semaphore. If no more tasks are allowed to - * acquire the semaphore, calling this function will put the task to sleep. - * If the sleep is interrupted by a signal, this function will return -EINTR. - * If the semaphore is successfully acquired, this function returns 0. - */ -int down_interruptible(struct semaphore *sem) -{ - unsigned long flags; - int result = 0; - - raw_spin_lock_irqsave(&sem->lock, flags); - if (likely(sem->count > 0)) - sem->count--; - else - result = __down_interruptible(sem); - raw_spin_unlock_irqrestore(&sem->lock, flags); - - return result; -} -EXPORT_SYMBOL(down_interruptible); - -/** - * down_killable - acquire the semaphore unless killed - * @sem: the semaphore to be acquired - * - * Attempts to acquire the semaphore. If no more tasks are allowed to - * acquire the semaphore, calling this function will put the task to sleep. - * If the sleep is interrupted by a fatal signal, this function will return - * -EINTR. If the semaphore is successfully acquired, this function returns - * 0. - */ -int down_killable(struct semaphore *sem) -{ - unsigned long flags; - int result = 0; - - raw_spin_lock_irqsave(&sem->lock, flags); - if (likely(sem->count > 0)) - sem->count--; - else - result = __down_killable(sem); - raw_spin_unlock_irqrestore(&sem->lock, flags); - - return result; -} -EXPORT_SYMBOL(down_killable); - -/** - * down_trylock - try to acquire the semaphore, without waiting - * @sem: the semaphore to be acquired - * - * Try to acquire the semaphore atomically. Returns 0 if the semaphore has - * been acquired successfully or 1 if it it cannot be acquired. - * - * NOTE: This return value is inverted from both spin_trylock and - * mutex_trylock! Be careful about this when converting code. - * - * Unlike mutex_trylock, this function can be used from interrupt context, - * and the semaphore can be released by any task or interrupt. - */ -int down_trylock(struct semaphore *sem) -{ - unsigned long flags; - int count; - - raw_spin_lock_irqsave(&sem->lock, flags); - count = sem->count - 1; - if (likely(count >= 0)) - sem->count = count; - raw_spin_unlock_irqrestore(&sem->lock, flags); - - return (count < 0); -} -EXPORT_SYMBOL(down_trylock); - -/** - * down_timeout - acquire the semaphore within a specified time - * @sem: the semaphore to be acquired - * @jiffies: how long to wait before failing - * - * Attempts to acquire the semaphore. If no more tasks are allowed to - * acquire the semaphore, calling this function will put the task to sleep. - * If the semaphore is not released within the specified number of jiffies, - * this function returns -ETIME. It returns 0 if the semaphore was acquired. - */ -int down_timeout(struct semaphore *sem, long jiffies) -{ - unsigned long flags; - int result = 0; - - raw_spin_lock_irqsave(&sem->lock, flags); - if (likely(sem->count > 0)) - sem->count--; - else - result = __down_timeout(sem, jiffies); - raw_spin_unlock_irqrestore(&sem->lock, flags); - - return result; -} -EXPORT_SYMBOL(down_timeout); - -/** - * up - release the semaphore - * @sem: the semaphore to release - * - * Release the semaphore. Unlike mutexes, up() may be called from any - * context and even by tasks which have never called down(). - */ -void up(struct semaphore *sem) -{ - unsigned long flags; - - raw_spin_lock_irqsave(&sem->lock, flags); - if (likely(list_empty(&sem->wait_list))) - sem->count++; - else - __up(sem); - raw_spin_unlock_irqrestore(&sem->lock, flags); -} -EXPORT_SYMBOL(up); - -/* Functions for the contended case */ - -struct semaphore_waiter { - struct list_head list; - struct task_struct *task; - bool up; -}; - -/* - * Because this function is inlined, the 'state' parameter will be - * constant, and thus optimised away by the compiler. Likewise the - * 'timeout' parameter for the cases without timeouts. - */ -static inline int __sched __down_common(struct semaphore *sem, long state, - long timeout) -{ - struct task_struct *task = current; - struct semaphore_waiter waiter; - - list_add_tail(&waiter.list, &sem->wait_list); - waiter.task = task; - waiter.up = false; - - for (;;) { - if (signal_pending_state(state, task)) - goto interrupted; - if (unlikely(timeout <= 0)) - goto timed_out; - __set_task_state(task, state); - raw_spin_unlock_irq(&sem->lock); - timeout = schedule_timeout(timeout); - raw_spin_lock_irq(&sem->lock); - if (waiter.up) - return 0; - } - - timed_out: - list_del(&waiter.list); - return -ETIME; - - interrupted: - list_del(&waiter.list); - return -EINTR; -} - -static noinline void __sched __down(struct semaphore *sem) -{ - __down_common(sem, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); -} - -static noinline int __sched __down_interruptible(struct semaphore *sem) -{ - return __down_common(sem, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); -} - -static noinline int __sched __down_killable(struct semaphore *sem) -{ - return __down_common(sem, TASK_KILLABLE, MAX_SCHEDULE_TIMEOUT); -} - -static noinline int __sched __down_timeout(struct semaphore *sem, long jiffies) -{ - return __down_common(sem, TASK_UNINTERRUPTIBLE, jiffies); -} - -static noinline void __sched __up(struct semaphore *sem) -{ - struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list, - struct semaphore_waiter, list); - list_del(&waiter->list); - waiter->up = true; - wake_up_process(waiter->task); -} -- cgit v0.10.2