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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/v850/kernel
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
downloadlinux-2.6.34-ux500-64ac24e738823161693bf791f87adc802cf529ff.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/v850/kernel')
-rw-r--r--arch/v850/kernel/Makefile2
-rw-r--r--arch/v850/kernel/semaphore.c166
-rw-r--r--arch/v850/kernel/v850_ksyms.c7
3 files changed, 1 insertions, 174 deletions
diff --git a/arch/v850/kernel/Makefile b/arch/v850/kernel/Makefile
index 3930482bddc..da5889c5357 100644
--- a/arch/v850/kernel/Makefile
+++ b/arch/v850/kernel/Makefile
@@ -11,7 +11,7 @@
extra-y := head.o init_task.o vmlinux.lds
-obj-y += intv.o entry.o process.o syscalls.o time.o semaphore.o setup.o \
+obj-y += intv.o entry.o process.o syscalls.o time.o setup.o \
signal.o irq.o mach.o ptrace.o bug.o
obj-$(CONFIG_MODULES) += module.o v850_ksyms.o
# chip-specific code
diff --git a/arch/v850/kernel/semaphore.c b/arch/v850/kernel/semaphore.c
deleted file mode 100644
index fc89fd661c9..00000000000
--- a/arch/v850/kernel/semaphore.c
+++ /dev/null
@@ -1,166 +0,0 @@
-/*
- * arch/v850/kernel/semaphore.c -- Semaphore support
- *
- * Copyright (C) 1998-2000 IBM Corporation
- * Copyright (C) 1999 Linus Torvalds
- *
- * This file is subject to the terms and conditions of the GNU General
- * Public License. See the file COPYING in the main directory of this
- * archive for more details.
- *
- * This file is a copy of the s390 version, arch/s390/kernel/semaphore.c
- * Author(s): Martin Schwidefsky
- * which was derived from the i386 version, linux/arch/i386/kernel/semaphore.c
- */
-
-#include <linux/errno.h>
-#include <linux/sched.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 semaphore spinlock.
- *
- * 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.
- */
-
-void __up(struct semaphore *sem)
-{
- wake_up(&sem->wait);
-}
-
-static DEFINE_SPINLOCK(semaphore_lock);
-
-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);
-
- spin_lock_irq(&semaphore_lock);
- sem->sleepers++;
- for (;;) {
- int sleepers = sem->sleepers;
-
- /*
- * Add "everybody else" into it. They aren't
- * playing, because we own the spinlock.
- */
- if (!atomic_add_negative(sleepers - 1, &sem->count)) {
- sem->sleepers = 0;
- break;
- }
- sem->sleepers = 1; /* us - see -1 above */
- spin_unlock_irq(&semaphore_lock);
-
- schedule();
- tsk->state = TASK_UNINTERRUPTIBLE;
- spin_lock_irq(&semaphore_lock);
- }
- spin_unlock_irq(&semaphore_lock);
- remove_wait_queue(&sem->wait, &wait);
- tsk->state = TASK_RUNNING;
- 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);
-
- spin_lock_irq(&semaphore_lock);
- 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. The
- * "-1" is because we're still hoping to get
- * the lock.
- */
- if (!atomic_add_negative(sleepers - 1, &sem->count)) {
- sem->sleepers = 0;
- break;
- }
- sem->sleepers = 1; /* us - see -1 above */
- spin_unlock_irq(&semaphore_lock);
-
- schedule();
- tsk->state = TASK_INTERRUPTIBLE;
- spin_lock_irq(&semaphore_lock);
- }
- spin_unlock_irq(&semaphore_lock);
- tsk->state = TASK_RUNNING;
- remove_wait_queue(&sem->wait, &wait);
- wake_up(&sem->wait);
- return retval;
-}
-
-/*
- * Trylock failed - make sure we correct for
- * having decremented the count.
- */
-int __down_trylock(struct semaphore * sem)
-{
- unsigned long flags;
- int sleepers;
-
- spin_lock_irqsave(&semaphore_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.
- */
- if (!atomic_add_negative(sleepers, &sem->count))
- wake_up(&sem->wait);
-
- spin_unlock_irqrestore(&semaphore_lock, flags);
- return 1;
-}
diff --git a/arch/v850/kernel/v850_ksyms.c b/arch/v850/kernel/v850_ksyms.c
index 93575fdc874..8d386a5dbc4 100644
--- a/arch/v850/kernel/v850_ksyms.c
+++ b/arch/v850/kernel/v850_ksyms.c
@@ -11,7 +11,6 @@
#include <asm/pgalloc.h>
#include <asm/irq.h>
#include <asm/io.h>
-#include <asm/semaphore.h>
#include <asm/checksum.h>
#include <asm/current.h>
@@ -34,12 +33,6 @@ EXPORT_SYMBOL (memset);
EXPORT_SYMBOL (memcpy);
EXPORT_SYMBOL (memmove);
-/* semaphores */
-EXPORT_SYMBOL (__down);
-EXPORT_SYMBOL (__down_interruptible);
-EXPORT_SYMBOL (__down_trylock);
-EXPORT_SYMBOL (__up);
-
/*
* libgcc functions - functions that are used internally by the
* compiler... (prototypes are not correct though, but that