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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/m32r/kernel
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
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/m32r/kernel')
-rw-r--r--arch/m32r/kernel/Makefile2
-rw-r--r--arch/m32r/kernel/m32r_ksyms.c5
-rw-r--r--arch/m32r/kernel/semaphore.c185
3 files changed, 1 insertions, 191 deletions
diff --git a/arch/m32r/kernel/Makefile b/arch/m32r/kernel/Makefile
index e97e26e87c9..09200d4886e 100644
--- a/arch/m32r/kernel/Makefile
+++ b/arch/m32r/kernel/Makefile
@@ -5,7 +5,7 @@
extra-y := head.o init_task.o vmlinux.lds
obj-y := process.o entry.o traps.o align.o irq.o setup.o time.o \
- m32r_ksyms.o sys_m32r.o semaphore.o signal.o ptrace.o
+ m32r_ksyms.o sys_m32r.o signal.o ptrace.o
obj-$(CONFIG_SMP) += smp.o smpboot.o
obj-$(CONFIG_MODULES) += module.o
diff --git a/arch/m32r/kernel/m32r_ksyms.c b/arch/m32r/kernel/m32r_ksyms.c
index 41a4c95e06d..e6709fe950b 100644
--- a/arch/m32r/kernel/m32r_ksyms.c
+++ b/arch/m32r/kernel/m32r_ksyms.c
@@ -7,7 +7,6 @@
#include <linux/interrupt.h>
#include <linux/string.h>
-#include <asm/semaphore.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/checksum.h>
@@ -22,10 +21,6 @@ EXPORT_SYMBOL(dump_fpu);
EXPORT_SYMBOL(__ioremap);
EXPORT_SYMBOL(iounmap);
EXPORT_SYMBOL(kernel_thread);
-EXPORT_SYMBOL(__down);
-EXPORT_SYMBOL(__down_interruptible);
-EXPORT_SYMBOL(__up);
-EXPORT_SYMBOL(__down_trylock);
/* Networking helper routines. */
/* Delay loops */
diff --git a/arch/m32r/kernel/semaphore.c b/arch/m32r/kernel/semaphore.c
deleted file mode 100644
index 940c2d37cfd..00000000000
--- a/arch/m32r/kernel/semaphore.c
+++ /dev/null
@@ -1,185 +0,0 @@
-/*
- * linux/arch/m32r/semaphore.c
- * orig : i386 2.6.4
- *
- * M32R semaphore implementation.
- *
- * Copyright (c) 2002 - 2004 Hitoshi Yamamoto
- */
-
-/*
- * i386 semaphore implementation.
- *
- * (C) Copyright 1999 Linus Torvalds
- *
- * Portions Copyright 1999 Red Hat, Inc.
- *
- * 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.
- *
- * rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org>
- */
-#include <linux/sched.h>
-#include <linux/err.h>
-#include <linux/init.h>
-#include <asm/semaphore.h>
-
-/*
- * 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 <asm/semaphore.h>
- * 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.
- */
-
-asmlinkage void __up(struct semaphore *sem)
-{
- wake_up(&sem->wait);
-}
-
-asmlinkage 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_negative(sleepers - 1, &sem->count)) {
- 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;
-}
-
-asmlinkage 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
- * wait_queue_head. The "-1" is because we're
- * still hoping to get the semaphore.
- */
- if (!atomic_add_negative(sleepers - 1, &sem->count)) {
- 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;
-}
-
-/*
- * Trylock failed - make sure we correct for
- * having decremented the count.
- *
- * We could have done the trylock with a
- * single "cmpxchg" without failure cases,
- * but then it wouldn't work on a 386.
- */
-asmlinkage int __down_trylock(struct semaphore * sem)
-{
- int sleepers;
- unsigned long flags;
-
- spin_lock_irqsave(&sem->wait.lock, flags);
- sleepers = sem->sleepers + 1;
- sem->sleepers = 0;
-
- /*
- * Add "everybody else" and us into it. They aren't
- * playing, because we own the spinlock in the
- * wait_queue_head.
- */
- if (!atomic_add_negative(sleepers, &sem->count)) {
- wake_up_locked(&sem->wait);
- }
-
- spin_unlock_irqrestore(&sem->wait.lock, flags);
- return 1;
-}