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authorMatthew Wilcox <matthew@wil.cx>2008-03-07 21:55:58 -0500
committerMatthew Wilcox <willy@linux.intel.com>2008-04-17 10:42:34 -0400
commit64ac24e738823161693bf791f87adc802cf529ff (patch)
tree19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/mn10300
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
downloadop-kernel-dev-64ac24e738823161693bf791f87adc802cf529ff.zip
op-kernel-dev-64ac24e738823161693bf791f87adc802cf529ff.tar.gz
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')
-rw-r--r--arch/mn10300/kernel/Makefile2
-rw-r--r--arch/mn10300/kernel/semaphore.c149
2 files changed, 1 insertions, 150 deletions
diff --git a/arch/mn10300/kernel/Makefile b/arch/mn10300/kernel/Makefile
index ef07c95..23f2ab6 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 9153c40..0000000
--- 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);
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