diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-18 08:25:29 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-18 08:25:29 -0700 |
commit | d7bb545d86825e635cab33a1dd81ca0ad7b92887 (patch) | |
tree | 34da4139ef06ceab6549aea3906639c7413978c8 /arch/ia64/kernel/semaphore.c | |
parent | 75e98b34155264d943aa53edce465e87f3ccbadf (diff) | |
parent | 2342e51ba2b52a7f5b78227e6faa4603ed3632a0 (diff) |
Merge branch 'semaphore' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc
* 'semaphore' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc:
Remove DEBUG_SEMAPHORE from Kconfig
Improve semaphore documentation
Simplify semaphore implementation
Add down_timeout and change ACPI to use it
Introduce down_killable()
Generic semaphore implementation
Add semaphore.h to kernel_lock.c
Fix quota.h includes
Diffstat (limited to 'arch/ia64/kernel/semaphore.c')
-rw-r--r-- | arch/ia64/kernel/semaphore.c | 165 |
1 files changed, 0 insertions, 165 deletions
diff --git a/arch/ia64/kernel/semaphore.c b/arch/ia64/kernel/semaphore.c deleted file mode 100644 index 2724ef3fbae..00000000000 --- a/arch/ia64/kernel/semaphore.c +++ /dev/null @@ -1,165 +0,0 @@ -/* - * IA-64 semaphore implementation (derived from x86 version). - * - * Copyright (C) 1999-2000, 2002 Hewlett-Packard Co - * David Mosberger-Tang <davidm@hpl.hp.com> - */ - -/* - * Semaphores are implemented using a two-way counter: The "count" - * variable is decremented for each process that tries to acquire the - * semaphore, while the "sleepers" variable is a count of such - * acquires. - * - * Notably, the inline "up()" and "down()" functions can efficiently - * test if they need to do any extra work (up needs to do something - * only if count was negative before the increment operation. - * - * "sleeping" and the contention routine ordering is protected - * by the spinlock in the semaphore's waitqueue head. - * - * Note that these functions are only called when there is contention - * on the lock, and as such all this is the "non-critical" part of the - * whole semaphore business. The critical part is the inline stuff in - * <asm/semaphore.h> where we want to avoid any extra jumps and calls. - */ -#include <linux/sched.h> -#include <linux/init.h> - -#include <asm/errno.h> -#include <asm/semaphore.h> - -/* - * Logic: - * - Only on a boundary condition do we need to care. When we go - * from a negative count to a non-negative, we wake people up. - * - When we go from a non-negative count to a negative do we - * (a) synchronize with the "sleepers" count and (b) make sure - * that we're on the wakeup list before we synchronize so that - * we cannot lose wakeup events. - */ - -void -__up (struct semaphore *sem) -{ - wake_up(&sem->wait); -} - -void __sched __down (struct semaphore *sem) -{ - struct task_struct *tsk = current; - DECLARE_WAITQUEUE(wait, tsk); - unsigned long flags; - - tsk->state = TASK_UNINTERRUPTIBLE; - spin_lock_irqsave(&sem->wait.lock, flags); - add_wait_queue_exclusive_locked(&sem->wait, &wait); - - sem->sleepers++; - for (;;) { - int sleepers = sem->sleepers; - - /* - * Add "everybody else" into it. They aren't - * playing, because we own the spinlock in - * the wait_queue_head. - */ - if (!atomic_add_negative(sleepers - 1, &sem->count)) { - sem->sleepers = 0; - break; - } - sem->sleepers = 1; /* us - see -1 above */ - spin_unlock_irqrestore(&sem->wait.lock, flags); - - schedule(); - - spin_lock_irqsave(&sem->wait.lock, flags); - tsk->state = TASK_UNINTERRUPTIBLE; - } - remove_wait_queue_locked(&sem->wait, &wait); - wake_up_locked(&sem->wait); - spin_unlock_irqrestore(&sem->wait.lock, flags); - tsk->state = TASK_RUNNING; -} - -int __sched __down_interruptible (struct semaphore * sem) -{ - int retval = 0; - struct task_struct *tsk = current; - DECLARE_WAITQUEUE(wait, tsk); - unsigned long flags; - - tsk->state = TASK_INTERRUPTIBLE; - spin_lock_irqsave(&sem->wait.lock, flags); - add_wait_queue_exclusive_locked(&sem->wait, &wait); - - sem->sleepers ++; - for (;;) { - int sleepers = sem->sleepers; - - /* - * With signals pending, this turns into - * the trylock failure case - we won't be - * sleeping, and we* can't get the lock as - * it has contention. Just correct the count - * and exit. - */ - if (signal_pending(current)) { - retval = -EINTR; - sem->sleepers = 0; - atomic_add(sleepers, &sem->count); - break; - } - - /* - * Add "everybody else" into it. They aren't - * playing, because we own the spinlock in - * wait_queue_head. The "-1" is because we're - * still hoping to get the semaphore. - */ - if (!atomic_add_negative(sleepers - 1, &sem->count)) { - sem->sleepers = 0; - break; - } - sem->sleepers = 1; /* us - see -1 above */ - spin_unlock_irqrestore(&sem->wait.lock, flags); - - schedule(); - - spin_lock_irqsave(&sem->wait.lock, flags); - tsk->state = TASK_INTERRUPTIBLE; - } - remove_wait_queue_locked(&sem->wait, &wait); - wake_up_locked(&sem->wait); - spin_unlock_irqrestore(&sem->wait.lock, flags); - - tsk->state = TASK_RUNNING; - return retval; -} - -/* - * Trylock failed - make sure we correct for having decremented the - * count. - */ -int -__down_trylock (struct semaphore *sem) -{ - unsigned long flags; - int sleepers; - - spin_lock_irqsave(&sem->wait.lock, flags); - sleepers = sem->sleepers + 1; - sem->sleepers = 0; - - /* - * Add "everybody else" and us into it. They aren't - * playing, because we own the spinlock in the - * wait_queue_head. - */ - if (!atomic_add_negative(sleepers, &sem->count)) { - wake_up_locked(&sem->wait); - } - - spin_unlock_irqrestore(&sem->wait.lock, flags); - return 1; -} |