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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/parisc
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/parisc')
-rw-r--r--arch/parisc/kernel/Makefile2
-rw-r--r--arch/parisc/kernel/parisc_ksyms.c5
-rw-r--r--arch/parisc/kernel/semaphore.c102
3 files changed, 1 insertions, 108 deletions
diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index 27827bc3717..1f6585a56f9 100644
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -9,7 +9,7 @@ AFLAGS_pacache.o := -traditional
obj-y := cache.o pacache.o setup.o traps.o time.o irq.o \
pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \
- ptrace.o hardware.o inventory.o drivers.o semaphore.o \
+ ptrace.o hardware.o inventory.o drivers.o \
signal.o hpmc.o real2.o parisc_ksyms.o unaligned.o \
process.o processor.o pdc_cons.o pdc_chassis.o unwind.o \
topology.o
diff --git a/arch/parisc/kernel/parisc_ksyms.c b/arch/parisc/kernel/parisc_ksyms.c
index 7aca704e96f..5b7fc4aa044 100644
--- a/arch/parisc/kernel/parisc_ksyms.c
+++ b/arch/parisc/kernel/parisc_ksyms.c
@@ -69,11 +69,6 @@ EXPORT_SYMBOL(memcpy_toio);
EXPORT_SYMBOL(memcpy_fromio);
EXPORT_SYMBOL(memset_io);
-#include <asm/semaphore.h>
-EXPORT_SYMBOL(__up);
-EXPORT_SYMBOL(__down_interruptible);
-EXPORT_SYMBOL(__down);
-
extern void $$divI(void);
extern void $$divU(void);
extern void $$remI(void);
diff --git a/arch/parisc/kernel/semaphore.c b/arch/parisc/kernel/semaphore.c
deleted file mode 100644
index ee806bcc372..00000000000
--- a/arch/parisc/kernel/semaphore.c
+++ /dev/null
@@ -1,102 +0,0 @@
-/*
- * Semaphore implementation Copyright (c) 2001 Matthew Wilcox, Hewlett-Packard
- */
-
-#include <linux/sched.h>
-#include <linux/spinlock.h>
-#include <linux/errno.h>
-#include <linux/init.h>
-
-/*
- * Semaphores are complex as we wish to avoid using two variables.
- * `count' has multiple roles, depending on its value. If it is positive
- * or zero, there are no waiters. The functions here will never be
- * called; see <asm/semaphore.h>
- *
- * When count is -1 it indicates there is at least one task waiting
- * for the semaphore.
- *
- * When count is less than that, there are '- count - 1' wakeups
- * pending. ie if it has value -3, there are 2 wakeups pending.
- *
- * 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.
- */
-void __up(struct semaphore *sem)
-{
- sem->count--;
- wake_up(&sem->wait);
-}
-
-#define wakers(count) (-1 - count)
-
-#define DOWN_HEAD \
- int ret = 0; \
- DECLARE_WAITQUEUE(wait, current); \
- \
- /* Note that someone is waiting */ \
- if (sem->count == 0) \
- sem->count = -1; \
- \
- /* protected by the sentry still -- use unlocked version */ \
- wait.flags = WQ_FLAG_EXCLUSIVE; \
- __add_wait_queue_tail(&sem->wait, &wait); \
- lost_race: \
- spin_unlock_irq(&sem->sentry); \
-
-#define DOWN_TAIL \
- spin_lock_irq(&sem->sentry); \
- if (wakers(sem->count) == 0 && ret == 0) \
- goto lost_race; /* Someone stole our wakeup */ \
- __remove_wait_queue(&sem->wait, &wait); \
- current->state = TASK_RUNNING; \
- if (!waitqueue_active(&sem->wait) && (sem->count < 0)) \
- sem->count = wakers(sem->count);
-
-#define UPDATE_COUNT \
- sem->count += (sem->count < 0) ? 1 : - 1;
-
-
-void __sched __down(struct semaphore * sem)
-{
- DOWN_HEAD
-
- for(;;) {
- set_task_state(current, TASK_UNINTERRUPTIBLE);
- /* we can _read_ this without the sentry */
- if (sem->count != -1)
- break;
- schedule();
- }
-
- DOWN_TAIL
- UPDATE_COUNT
-}
-
-int __sched __down_interruptible(struct semaphore * sem)
-{
- DOWN_HEAD
-
- for(;;) {
- set_task_state(current, TASK_INTERRUPTIBLE);
- /* we can _read_ this without the sentry */
- if (sem->count != -1)
- break;
-
- if (signal_pending(current)) {
- ret = -EINTR;
- break;
- }
- schedule();
- }
-
- DOWN_TAIL
-
- if (!ret) {
- UPDATE_COUNT
- }
-
- return ret;
-}