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author | 2008-03-07 21:55:58 -0500 | |
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committer | 2008-04-17 10:42:34 -0400 | |
commit | 64ac24e738823161693bf791f87adc802cf529ff (patch) | |
tree | 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/mn10300/kernel | |
parent | Add semaphore.h to kernel_lock.c (diff) | |
download | linux-64ac24e738823161693bf791f87adc802cf529ff.tar.gz linux-64ac24e738823161693bf791f87adc802cf529ff.tar.bz2 linux-64ac24e738823161693bf791f87adc802cf529ff.zip |
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 <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/mn10300/kernel')
-rw-r--r-- | arch/mn10300/kernel/Makefile | 2 | ||||
-rw-r--r-- | arch/mn10300/kernel/semaphore.c | 149 |
2 files changed, 1 insertions, 150 deletions
diff --git a/arch/mn10300/kernel/Makefile b/arch/mn10300/kernel/Makefile index ef07c956170a..23f2ab67574c 100644 --- a/arch/mn10300/kernel/Makefile +++ b/arch/mn10300/kernel/Makefile @@ -3,7 +3,7 @@ # extra-y := head.o init_task.o vmlinux.lds -obj-y := process.o semaphore.o signal.o entry.o fpu.o traps.o irq.o \ +obj-y := process.o signal.o entry.o fpu.o traps.o irq.o \ ptrace.o setup.o time.o sys_mn10300.o io.o kthread.o \ switch_to.o mn10300_ksyms.o kernel_execve.o diff --git a/arch/mn10300/kernel/semaphore.c b/arch/mn10300/kernel/semaphore.c deleted file mode 100644 index 9153c4039fd2..000000000000 --- a/arch/mn10300/kernel/semaphore.c +++ /dev/null @@ -1,149 +0,0 @@ -/* MN10300 Semaphore implementation - * - * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. - * Written by David Howells (dhowells@redhat.com) - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public Licence - * as published by the Free Software Foundation; either version - * 2 of the Licence, or (at your option) any later version. - */ -#include <linux/sched.h> -#include <linux/module.h> -#include <asm/semaphore.h> - -struct sem_waiter { - struct list_head list; - struct task_struct *task; -}; - -#if SEMAPHORE_DEBUG -void semtrace(struct semaphore *sem, const char *str) -{ - if (sem->debug) - printk(KERN_DEBUG "[%d] %s({%d,%d})\n", - current->pid, - str, - atomic_read(&sem->count), - list_empty(&sem->wait_list) ? 0 : 1); -} -#else -#define semtrace(SEM, STR) do { } while (0) -#endif - -/* - * wait for a token to be granted from a semaphore - * - entered with lock held and interrupts disabled - */ -void __down(struct semaphore *sem, unsigned long flags) -{ - struct task_struct *tsk = current; - struct sem_waiter waiter; - - semtrace(sem, "Entering __down"); - - /* set up my own style of waitqueue */ - waiter.task = tsk; - get_task_struct(tsk); - - list_add_tail(&waiter.list, &sem->wait_list); - - /* we don't need to touch the semaphore struct anymore */ - spin_unlock_irqrestore(&sem->wait_lock, flags); - - /* wait to be given the semaphore */ - set_task_state(tsk, TASK_UNINTERRUPTIBLE); - - for (;;) { - if (!waiter.task) - break; - schedule(); - set_task_state(tsk, TASK_UNINTERRUPTIBLE); - } - - tsk->state = TASK_RUNNING; - semtrace(sem, "Leaving __down"); -} -EXPORT_SYMBOL(__down); - -/* - * interruptibly wait for a token to be granted from a semaphore - * - entered with lock held and interrupts disabled - */ -int __down_interruptible(struct semaphore *sem, unsigned long flags) -{ - struct task_struct *tsk = current; - struct sem_waiter waiter; - int ret; - - semtrace(sem, "Entering __down_interruptible"); - - /* set up my own style of waitqueue */ - waiter.task = tsk; - get_task_struct(tsk); - - list_add_tail(&waiter.list, &sem->wait_list); - - /* we don't need to touch the semaphore struct anymore */ - set_task_state(tsk, TASK_INTERRUPTIBLE); - - spin_unlock_irqrestore(&sem->wait_lock, flags); - - /* wait to be given the semaphore */ - ret = 0; - for (;;) { - if (!waiter.task) - break; - if (unlikely(signal_pending(current))) - goto interrupted; - schedule(); - set_task_state(tsk, TASK_INTERRUPTIBLE); - } - - out: - tsk->state = TASK_RUNNING; - semtrace(sem, "Leaving __down_interruptible"); - return ret; - - interrupted: - spin_lock_irqsave(&sem->wait_lock, flags); - list_del(&waiter.list); - spin_unlock_irqrestore(&sem->wait_lock, flags); - - ret = 0; - if (!waiter.task) { - put_task_struct(current); - ret = -EINTR; - } - goto out; -} -EXPORT_SYMBOL(__down_interruptible); - -/* - * release a single token back to a semaphore - * - entered with lock held and interrupts disabled - */ -void __up(struct semaphore *sem) -{ - struct task_struct *tsk; - struct sem_waiter *waiter; - - semtrace(sem, "Entering __up"); - - /* grant the token to the process at the front of the queue */ - waiter = list_entry(sem->wait_list.next, struct sem_waiter, list); - - /* We must be careful not to touch 'waiter' after we set ->task = NULL. - * It is an allocated on the waiter's stack and may become invalid at - * any time after that point (due to a wakeup from another source). - */ - list_del_init(&waiter->list); - tsk = waiter->task; - smp_mb(); - waiter->task = NULL; - wake_up_process(tsk); - put_task_struct(tsk); - - semtrace(sem, "Leaving __up"); -} -EXPORT_SYMBOL(__up); |