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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/ppc
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
downloadlinux-linaro-stable-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/ppc')
-rw-r--r--arch/ppc/kernel/semaphore.c131
1 files changed, 0 insertions, 131 deletions
diff --git a/arch/ppc/kernel/semaphore.c b/arch/ppc/kernel/semaphore.c
deleted file mode 100644
index 2fe429b27c14..000000000000
--- a/arch/ppc/kernel/semaphore.c
+++ /dev/null
@@ -1,131 +0,0 @@
-/*
- * PowerPC-specific semaphore code.
- *
- * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- *
- * April 2001 - Reworked by Paul Mackerras <paulus@samba.org>
- * to eliminate the SMP races in the old version between the updates
- * of `count' and `waking'. Now we use negative `count' values to
- * indicate that some process(es) are waiting for the semaphore.
- */
-
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <asm/atomic.h>
-#include <asm/semaphore.h>
-#include <asm/errno.h>
-
-/*
- * Atomically update sem->count.
- * This does the equivalent of the following:
- *
- * old_count = sem->count;
- * tmp = MAX(old_count, 0) + incr;
- * sem->count = tmp;
- * return old_count;
- */
-static inline int __sem_update_count(struct semaphore *sem, int incr)
-{
- int old_count, tmp;
-
- __asm__ __volatile__("\n"
-"1: lwarx %0,0,%3\n"
-" srawi %1,%0,31\n"
-" andc %1,%0,%1\n"
-" add %1,%1,%4\n"
- PPC405_ERR77(0,%3)
-" stwcx. %1,0,%3\n"
-" bne 1b"
- : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
- : "r" (&sem->count), "r" (incr), "m" (sem->count)
- : "cc");
-
- return old_count;
-}
-
-void __up(struct semaphore *sem)
-{
- /*
- * Note that we incremented count in up() before we came here,
- * but that was ineffective since the result was <= 0, and
- * any negative value of count is equivalent to 0.
- * This ends up setting count to 1, unless count is now > 0
- * (i.e. because some other cpu has called up() in the meantime),
- * in which case we just increment count.
- */
- __sem_update_count(sem, 1);
- wake_up(&sem->wait);
-}
-
-/*
- * Note that when we come in to __down or __down_interruptible,
- * we have already decremented count, but that decrement was
- * ineffective since the result was < 0, and any negative value
- * of count is equivalent to 0.
- * Thus it is only when we decrement count from some value > 0
- * that we have actually got the semaphore.
- */
-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);
- smp_wmb();
-
- /*
- * Try to get the semaphore. If the count is > 0, then we've
- * got the semaphore; we decrement count and exit the loop.
- * If the count is 0 or negative, we set it to -1, indicating
- * that we are asleep, and then sleep.
- */
- while (__sem_update_count(sem, -1) <= 0) {
- schedule();
- tsk->state = TASK_UNINTERRUPTIBLE;
- }
- remove_wait_queue(&sem->wait, &wait);
- tsk->state = TASK_RUNNING;
-
- /*
- * If there are any more sleepers, wake one of them up so
- * that it can either get the semaphore, or set count to -1
- * indicating that there are still processes sleeping.
- */
- 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);
- smp_wmb();
-
- while (__sem_update_count(sem, -1) <= 0) {
- if (signal_pending(current)) {
- /*
- * A signal is pending - give up trying.
- * Set sem->count to 0 if it is negative,
- * since we are no longer sleeping.
- */
- __sem_update_count(sem, 0);
- retval = -EINTR;
- break;
- }
- schedule();
- tsk->state = TASK_INTERRUPTIBLE;
- }
- tsk->state = TASK_RUNNING;
- remove_wait_queue(&sem->wait, &wait);
- wake_up(&sem->wait);
- return retval;
-}