diff options
author | Matthew Wilcox <matthew@wil.cx> | 2008-03-08 02:55:58 (GMT) |
---|---|---|
committer | Matthew Wilcox <willy@linux.intel.com> | 2008-04-17 14:42:34 (GMT) |
commit | 64ac24e738823161693bf791f87adc802cf529ff (patch) | |
tree | 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/sparc/kernel | |
parent | e48b3deee475134585eed03e7afebe4bf9e0dba9 (diff) | |
download | linux-fsl-qoriq-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/sparc/kernel')
-rw-r--r-- | arch/sparc/kernel/Makefile | 2 | ||||
-rw-r--r-- | arch/sparc/kernel/semaphore.c | 155 | ||||
-rw-r--r-- | arch/sparc/kernel/sparc_ksyms.c | 5 |
3 files changed, 1 insertions, 161 deletions
diff --git a/arch/sparc/kernel/Makefile b/arch/sparc/kernel/Makefile index bf1b15d..2712bb1 100644 --- a/arch/sparc/kernel/Makefile +++ b/arch/sparc/kernel/Makefile @@ -12,7 +12,7 @@ obj-y := entry.o wof.o wuf.o etrap.o rtrap.o traps.o $(IRQ_OBJS) \ sys_sparc.o sunos_asm.o systbls.o \ time.o windows.o cpu.o devices.o sclow.o \ tadpole.o tick14.o ptrace.o sys_solaris.o \ - unaligned.o una_asm.o muldiv.o semaphore.o \ + unaligned.o una_asm.o muldiv.o \ prom.o of_device.o devres.o devres-y = ../../../kernel/irq/devres.o diff --git a/arch/sparc/kernel/semaphore.c b/arch/sparc/kernel/semaphore.c deleted file mode 100644 index 0c37c1a..0000000 --- a/arch/sparc/kernel/semaphore.c +++ /dev/null @@ -1,155 +0,0 @@ -/* $Id: semaphore.c,v 1.7 2001/04/18 21:06:05 davem Exp $ */ - -/* sparc32 semaphore implementation, based on i386 version */ - -#include <linux/sched.h> -#include <linux/errno.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 (!atomic24_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; - atomic24_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 (!atomic24_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) -{ - int sleepers; - unsigned long flags; - - 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 (!atomic24_add_negative(sleepers, &sem->count)) - wake_up(&sem->wait); - - spin_unlock_irqrestore(&semaphore_lock, flags); - return 1; -} diff --git a/arch/sparc/kernel/sparc_ksyms.c b/arch/sparc/kernel/sparc_ksyms.c index c1025e5..97b1de0 100644 --- a/arch/sparc/kernel/sparc_ksyms.c +++ b/arch/sparc/kernel/sparc_ksyms.c @@ -107,11 +107,6 @@ EXPORT_SYMBOL(___rw_read_try); EXPORT_SYMBOL(___rw_read_exit); EXPORT_SYMBOL(___rw_write_enter); #endif -/* semaphores */ -EXPORT_SYMBOL(__up); -EXPORT_SYMBOL(__down); -EXPORT_SYMBOL(__down_trylock); -EXPORT_SYMBOL(__down_interruptible); EXPORT_SYMBOL(sparc_valid_addr_bitmap); EXPORT_SYMBOL(phys_base); |