From 64ac24e738823161693bf791f87adc802cf529ff Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 7 Mar 2008 21:55:58 -0500 Subject: 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 Acked-by: Ingo Molnar --- arch/parisc/kernel/Makefile | 2 +- arch/parisc/kernel/parisc_ksyms.c | 5 -- arch/parisc/kernel/semaphore.c | 102 -------------------------------------- 3 files changed, 1 insertion(+), 108 deletions(-) delete mode 100644 arch/parisc/kernel/semaphore.c (limited to 'arch/parisc') 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 -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 -#include -#include -#include - -/* - * 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 - * - * 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 - * 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; -} -- cgit v1.2.3