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authorMatthew Wilcox <matthew@wil.cx>2008-03-08 05:55:58 +0300
committerMatthew Wilcox <willy@linux.intel.com>2008-04-17 18:42:34 +0400
commit64ac24e738823161693bf791f87adc802cf529ff (patch)
tree19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/mips
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
downloadlinux-64ac24e738823161693bf791f87adc802cf529ff.tar.xz
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/mips')
-rw-r--r--arch/mips/kernel/Makefile2
-rw-r--r--arch/mips/kernel/semaphore.c168
2 files changed, 1 insertions, 169 deletions
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 9e78e1a4ca17..6fcdb6fda2e2 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -5,7 +5,7 @@
extra-y := head.o init_task.o vmlinux.lds
obj-y += cpu-probe.o branch.o entry.o genex.o irq.o process.o \
- ptrace.o reset.o semaphore.o setup.o signal.o syscall.o \
+ ptrace.o reset.o setup.o signal.o syscall.o \
time.o topology.o traps.o unaligned.o
obj-$(CONFIG_CEVT_BCM1480) += cevt-bcm1480.o
diff --git a/arch/mips/kernel/semaphore.c b/arch/mips/kernel/semaphore.c
deleted file mode 100644
index 1265358cdca1..000000000000
--- a/arch/mips/kernel/semaphore.c
+++ /dev/null
@@ -1,168 +0,0 @@
-/*
- * MIPS-specific semaphore code.
- *
- * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
- * Copyright (C) 2004 Ralf Baechle <ralf@linux-mips.org>
- *
- * 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/module.h>
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <asm/atomic.h>
-#include <asm/cpu-features.h>
-#include <asm/errno.h>
-#include <asm/semaphore.h>
-#include <asm/war.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;
- *
- * On machines without lld/scd we need a spinlock to make the manipulation of
- * sem->count and sem->waking atomic. Scalability isn't an issue because
- * this lock is used on UP only so it's just an empty variable.
- */
-static inline int __sem_update_count(struct semaphore *sem, int incr)
-{
- int old_count, tmp;
-
- if (cpu_has_llsc && R10000_LLSC_WAR) {
- __asm__ __volatile__(
- " .set mips3 \n"
- "1: ll %0, %2 # __sem_update_count \n"
- " sra %1, %0, 31 \n"
- " not %1 \n"
- " and %1, %0, %1 \n"
- " addu %1, %1, %3 \n"
- " sc %1, %2 \n"
- " beqzl %1, 1b \n"
- " .set mips0 \n"
- : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
- : "r" (incr), "m" (sem->count));
- } else if (cpu_has_llsc) {
- __asm__ __volatile__(
- " .set mips3 \n"
- "1: ll %0, %2 # __sem_update_count \n"
- " sra %1, %0, 31 \n"
- " not %1 \n"
- " and %1, %0, %1 \n"
- " addu %1, %1, %3 \n"
- " sc %1, %2 \n"
- " beqz %1, 1b \n"
- " .set mips0 \n"
- : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
- : "r" (incr), "m" (sem->count));
- } else {
- static DEFINE_SPINLOCK(semaphore_lock);
- unsigned long flags;
-
- spin_lock_irqsave(&semaphore_lock, flags);
- old_count = atomic_read(&sem->count);
- tmp = max_t(int, old_count, 0) + incr;
- atomic_set(&sem->count, tmp);
- spin_unlock_irqrestore(&semaphore_lock, flags);
- }
-
- 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);
-}
-
-EXPORT_SYMBOL(__up);
-
-/*
- * 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);
-
- __set_task_state(tsk, TASK_UNINTERRUPTIBLE);
- add_wait_queue_exclusive(&sem->wait, &wait);
-
- /*
- * 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();
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
- }
- remove_wait_queue(&sem->wait, &wait);
- __set_task_state(tsk, 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);
-}
-
-EXPORT_SYMBOL(__down);
-
-int __sched __down_interruptible(struct semaphore * sem)
-{
- int retval = 0;
- struct task_struct *tsk = current;
- DECLARE_WAITQUEUE(wait, tsk);
-
- __set_task_state(tsk, TASK_INTERRUPTIBLE);
- add_wait_queue_exclusive(&sem->wait, &wait);
-
- 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();
- set_task_state(tsk, TASK_INTERRUPTIBLE);
- }
- remove_wait_queue(&sem->wait, &wait);
- __set_task_state(tsk, TASK_RUNNING);
-
- wake_up(&sem->wait);
- return retval;
-}
-
-EXPORT_SYMBOL(__down_interruptible);