From 64ac24e738823161693bf791f87adc802cf529ff Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 7 Mar 2008 21:55:58 -0500 Subject: Generic semaphore implementation Semaphores are no longer performance-critical, so a generic C implementation is better for maintainability, debuggability and extensibility. Thanks to Peter Zijlstra for fixing the lockdep warning. Thanks to Harvey Harrison for pointing out that the unlikely() was unnecessary. Signed-off-by: Matthew Wilcox Acked-by: Ingo Molnar --- arch/v850/kernel/Makefile | 2 +- arch/v850/kernel/semaphore.c | 166 ------------------------------------------ arch/v850/kernel/v850_ksyms.c | 7 -- 3 files changed, 1 insertion(+), 174 deletions(-) delete mode 100644 arch/v850/kernel/semaphore.c (limited to 'arch/v850/kernel') diff --git a/arch/v850/kernel/Makefile b/arch/v850/kernel/Makefile index 3930482bddc4..da5889c53576 100644 --- a/arch/v850/kernel/Makefile +++ b/arch/v850/kernel/Makefile @@ -11,7 +11,7 @@ extra-y := head.o init_task.o vmlinux.lds -obj-y += intv.o entry.o process.o syscalls.o time.o semaphore.o setup.o \ +obj-y += intv.o entry.o process.o syscalls.o time.o setup.o \ signal.o irq.o mach.o ptrace.o bug.o obj-$(CONFIG_MODULES) += module.o v850_ksyms.o # chip-specific code diff --git a/arch/v850/kernel/semaphore.c b/arch/v850/kernel/semaphore.c deleted file mode 100644 index fc89fd661c99..000000000000 --- a/arch/v850/kernel/semaphore.c +++ /dev/null @@ -1,166 +0,0 @@ -/* - * arch/v850/kernel/semaphore.c -- Semaphore support - * - * Copyright (C) 1998-2000 IBM Corporation - * Copyright (C) 1999 Linus Torvalds - * - * This file is subject to the terms and conditions of the GNU General - * Public License. See the file COPYING in the main directory of this - * archive for more details. - * - * This file is a copy of the s390 version, arch/s390/kernel/semaphore.c - * Author(s): Martin Schwidefsky - * which was derived from the i386 version, linux/arch/i386/kernel/semaphore.c - */ - -#include -#include -#include - -#include - -/* - * Semaphores are implemented using a two-way counter: - * The "count" variable is decremented for each process - * that tries to acquire the semaphore, while the "sleeping" - * 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 semaphore spinlock. - * - * 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 - * where we want to avoid any extra jumps and calls. - */ - -/* - * 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 "sleeper" 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); -} - -static DEFINE_SPINLOCK(semaphore_lock); - -void __sched __down(struct semaphore * sem) -{ - struct task_struct *tsk = current; - DECLARE_WAITQUEUE(wait, tsk); - tsk->state = TASK_UNINTERRUPTIBLE; - add_wait_queue_exclusive(&sem->wait, &wait); - - spin_lock_irq(&semaphore_lock); - sem->sleepers++; - for (;;) { - int sleepers = sem->sleepers; - - /* - * Add "everybody else" into it. They aren't - * playing, because we own the spinlock. - */ - if (!atomic_add_negative(sleepers - 1, &sem->count)) { - sem->sleepers = 0; - break; - } - sem->sleepers = 1; /* us - see -1 above */ - spin_unlock_irq(&semaphore_lock); - - schedule(); - tsk->state = TASK_UNINTERRUPTIBLE; - spin_lock_irq(&semaphore_lock); - } - spin_unlock_irq(&semaphore_lock); - remove_wait_queue(&sem->wait, &wait); - tsk->state = TASK_RUNNING; - wake_up(&sem->wait); -} - -int __sched __down_interruptible(struct semaphore * sem) -{ - int retval = 0; - struct task_struct *tsk = current; - DECLARE_WAITQUEUE(wait, tsk); - tsk->state = TASK_INTERRUPTIBLE; - add_wait_queue_exclusive(&sem->wait, &wait); - - spin_lock_irq(&semaphore_lock); - 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. The - * "-1" is because we're still hoping to get - * the lock. - */ - if (!atomic_add_negative(sleepers - 1, &sem->count)) { - sem->sleepers = 0; - break; - } - sem->sleepers = 1; /* us - see -1 above */ - spin_unlock_irq(&semaphore_lock); - - schedule(); - tsk->state = TASK_INTERRUPTIBLE; - spin_lock_irq(&semaphore_lock); - } - spin_unlock_irq(&semaphore_lock); - tsk->state = TASK_RUNNING; - remove_wait_queue(&sem->wait, &wait); - wake_up(&sem->wait); - 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(&semaphore_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. - */ - if (!atomic_add_negative(sleepers, &sem->count)) - wake_up(&sem->wait); - - spin_unlock_irqrestore(&semaphore_lock, flags); - return 1; -} diff --git a/arch/v850/kernel/v850_ksyms.c b/arch/v850/kernel/v850_ksyms.c index 93575fdc874d..8d386a5dbc4a 100644 --- a/arch/v850/kernel/v850_ksyms.c +++ b/arch/v850/kernel/v850_ksyms.c @@ -11,7 +11,6 @@ #include #include #include -#include #include #include @@ -34,12 +33,6 @@ EXPORT_SYMBOL (memset); EXPORT_SYMBOL (memcpy); EXPORT_SYMBOL (memmove); -/* semaphores */ -EXPORT_SYMBOL (__down); -EXPORT_SYMBOL (__down_interruptible); -EXPORT_SYMBOL (__down_trylock); -EXPORT_SYMBOL (__up); - /* * libgcc functions - functions that are used internally by the * compiler... (prototypes are not correct though, but that -- cgit v1.2.3-59-g8ed1b