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/avr32/kernel/Makefile | 2 +- arch/avr32/kernel/semaphore.c | 148 ------------------------------------------ 2 files changed, 1 insertion(+), 149 deletions(-) delete mode 100644 arch/avr32/kernel/semaphore.c (limited to 'arch/avr32/kernel') diff --git a/arch/avr32/kernel/Makefile b/arch/avr32/kernel/Makefile index e4b6d122b03..18229d0d186 100644 --- a/arch/avr32/kernel/Makefile +++ b/arch/avr32/kernel/Makefile @@ -6,7 +6,7 @@ extra-y := head.o vmlinux.lds obj-$(CONFIG_SUBARCH_AVR32B) += entry-avr32b.o obj-y += syscall_table.o syscall-stubs.o irq.o -obj-y += setup.o traps.o semaphore.o ocd.o ptrace.o +obj-y += setup.o traps.o ocd.o ptrace.o obj-y += signal.o sys_avr32.o process.o time.o obj-y += init_task.o switch_to.o cpu.o obj-$(CONFIG_MODULES) += module.o avr32_ksyms.o diff --git a/arch/avr32/kernel/semaphore.c b/arch/avr32/kernel/semaphore.c deleted file mode 100644 index 1e2705a0501..00000000000 --- a/arch/avr32/kernel/semaphore.c +++ /dev/null @@ -1,148 +0,0 @@ -/* - * AVR32 sempahore implementation. - * - * Copyright (C) 2004-2006 Atmel Corporation - * - * Based on linux/arch/i386/kernel/semaphore.c - * Copyright (C) 1999 Linus Torvalds - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - */ - -#include -#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 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 - * 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); -} -EXPORT_SYMBOL(__up); - -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_return(sleepers - 1, &sem->count) >= 0) { - 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; -} -EXPORT_SYMBOL(__down); - -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 - * the wait_queue_head. - */ - if (atomic_add_return(sleepers - 1, &sem->count) >= 0) { - 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; -} -EXPORT_SYMBOL(__down_interruptible); -- cgit v1.2.3