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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 <[email protected]> Acked-by: Ingo Molnar <[email protected]>
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Matthew Wilcox
Matthew Wilcox
parent
e48b3deee4
commit
64ac24e738
113 changed files with 314 additions and 7679 deletions
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#ifndef _M68K_SEMAPHORE_HELPER_H
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#define _M68K_SEMAPHORE_HELPER_H
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/*
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* SMP- and interrupt-safe semaphores helper functions.
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*
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* (C) Copyright 1996 Linus Torvalds
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*
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* m68k version by Andreas Schwab
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*/
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#include <linux/errno.h>
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/*
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* These two _must_ execute atomically wrt each other.
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*/
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static inline void wake_one_more(struct semaphore * sem)
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{
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atomic_inc(&sem->waking);
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}
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#ifndef CONFIG_RMW_INSNS
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extern spinlock_t semaphore_wake_lock;
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#endif
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static inline int waking_non_zero(struct semaphore *sem)
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{
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int ret;
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#ifndef CONFIG_RMW_INSNS
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unsigned long flags;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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ret = 0;
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if (atomic_read(&sem->waking) > 0) {
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atomic_dec(&sem->waking);
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ret = 1;
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}
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spin_unlock_irqrestore(&semaphore_wake_lock, flags);
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#else
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int tmp1, tmp2;
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__asm__ __volatile__
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("1: movel %1,%2\n"
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" jle 2f\n"
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" subql #1,%2\n"
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" casl %1,%2,%3\n"
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" jne 1b\n"
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" moveq #1,%0\n"
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"2:"
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: "=d" (ret), "=d" (tmp1), "=d" (tmp2)
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: "m" (sem->waking), "0" (0), "1" (sem->waking));
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#endif
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return ret;
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}
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/*
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* waking_non_zero_interruptible:
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* 1 got the lock
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* 0 go to sleep
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* -EINTR interrupted
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*/
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static inline int waking_non_zero_interruptible(struct semaphore *sem,
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struct task_struct *tsk)
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{
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int ret;
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#ifndef CONFIG_RMW_INSNS
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unsigned long flags;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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ret = 0;
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if (atomic_read(&sem->waking) > 0) {
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atomic_dec(&sem->waking);
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ret = 1;
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} else if (signal_pending(tsk)) {
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atomic_inc(&sem->count);
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ret = -EINTR;
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}
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spin_unlock_irqrestore(&semaphore_wake_lock, flags);
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#else
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int tmp1, tmp2;
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__asm__ __volatile__
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("1: movel %1,%2\n"
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" jle 2f\n"
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" subql #1,%2\n"
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" casl %1,%2,%3\n"
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" jne 1b\n"
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" moveq #1,%0\n"
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" jra %a4\n"
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"2:"
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: "=d" (ret), "=d" (tmp1), "=d" (tmp2)
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: "m" (sem->waking), "i" (&&next), "0" (0), "1" (sem->waking));
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if (signal_pending(tsk)) {
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atomic_inc(&sem->count);
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ret = -EINTR;
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}
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next:
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#endif
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return ret;
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}
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/*
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* waking_non_zero_trylock:
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* 1 failed to lock
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* 0 got the lock
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*/
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static inline int waking_non_zero_trylock(struct semaphore *sem)
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{
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int ret;
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#ifndef CONFIG_RMW_INSNS
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unsigned long flags;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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ret = 1;
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if (atomic_read(&sem->waking) > 0) {
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atomic_dec(&sem->waking);
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ret = 0;
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} else
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atomic_inc(&sem->count);
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spin_unlock_irqrestore(&semaphore_wake_lock, flags);
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#else
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int tmp1, tmp2;
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__asm__ __volatile__
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("1: movel %1,%2\n"
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" jle 2f\n"
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" subql #1,%2\n"
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" casl %1,%2,%3\n"
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" jne 1b\n"
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" moveq #0,%0\n"
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"2:"
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: "=d" (ret), "=d" (tmp1), "=d" (tmp2)
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: "m" (sem->waking), "0" (1), "1" (sem->waking));
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if (ret)
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atomic_inc(&sem->count);
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#endif
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return ret;
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}
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#endif
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@ -1,163 +1 @@
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#ifndef _M68K_SEMAPHORE_H
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#define _M68K_SEMAPHORE_H
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#define RW_LOCK_BIAS 0x01000000
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#ifndef __ASSEMBLY__
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#include <linux/linkage.h>
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#include <linux/wait.h>
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#include <linux/spinlock.h>
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#include <linux/rwsem.h>
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#include <linux/stringify.h>
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#include <asm/system.h>
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#include <asm/atomic.h>
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/*
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* Interrupt-safe semaphores..
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*
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* (C) Copyright 1996 Linus Torvalds
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*
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* m68k version by Andreas Schwab
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*/
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struct semaphore {
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atomic_t count;
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atomic_t waking;
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wait_queue_head_t wait;
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};
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#define __SEMAPHORE_INITIALIZER(name, n) \
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{ \
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.count = ATOMIC_INIT(n), \
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.waking = ATOMIC_INIT(0), \
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.wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
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}
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#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
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struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
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#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
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static inline void sema_init(struct semaphore *sem, int val)
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{
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*sem = (struct semaphore)__SEMAPHORE_INITIALIZER(*sem, val);
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}
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static inline void init_MUTEX (struct semaphore *sem)
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{
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sema_init(sem, 1);
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}
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static inline void init_MUTEX_LOCKED (struct semaphore *sem)
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{
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sema_init(sem, 0);
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}
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asmlinkage void __down_failed(void /* special register calling convention */);
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asmlinkage int __down_failed_interruptible(void /* params in registers */);
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asmlinkage int __down_failed_trylock(void /* params in registers */);
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asmlinkage void __up_wakeup(void /* special register calling convention */);
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asmlinkage void __down(struct semaphore * sem);
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asmlinkage int __down_interruptible(struct semaphore * sem);
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asmlinkage int __down_trylock(struct semaphore * sem);
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asmlinkage void __up(struct semaphore * sem);
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/*
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* This is ugly, but we want the default case to fall through.
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* "down_failed" is a special asm handler that calls the C
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* routine that actually waits. See arch/m68k/lib/semaphore.S
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*/
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static inline void down(struct semaphore *sem)
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{
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register struct semaphore *sem1 __asm__ ("%a1") = sem;
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might_sleep();
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__asm__ __volatile__(
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"| atomic down operation\n\t"
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"subql #1,%0@\n\t"
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"jmi 2f\n\t"
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"1:\n"
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LOCK_SECTION_START(".even\n\t")
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"2:\tpea 1b\n\t"
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"jbra __down_failed\n"
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LOCK_SECTION_END
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: /* no outputs */
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: "a" (sem1)
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: "memory");
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}
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static inline int down_interruptible(struct semaphore *sem)
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{
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register struct semaphore *sem1 __asm__ ("%a1") = sem;
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register int result __asm__ ("%d0");
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might_sleep();
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__asm__ __volatile__(
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"| atomic interruptible down operation\n\t"
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"subql #1,%1@\n\t"
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"jmi 2f\n\t"
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"clrl %0\n"
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"1:\n"
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LOCK_SECTION_START(".even\n\t")
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"2:\tpea 1b\n\t"
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"jbra __down_failed_interruptible\n"
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LOCK_SECTION_END
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: "=d" (result)
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: "a" (sem1)
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: "memory");
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return result;
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}
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static inline int down_trylock(struct semaphore *sem)
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{
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register struct semaphore *sem1 __asm__ ("%a1") = sem;
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register int result __asm__ ("%d0");
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__asm__ __volatile__(
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"| atomic down trylock operation\n\t"
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"subql #1,%1@\n\t"
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"jmi 2f\n\t"
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"clrl %0\n"
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"1:\n"
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LOCK_SECTION_START(".even\n\t")
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"2:\tpea 1b\n\t"
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"jbra __down_failed_trylock\n"
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LOCK_SECTION_END
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: "=d" (result)
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: "a" (sem1)
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: "memory");
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return result;
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}
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/*
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* Note! This is subtle. We jump to wake people up only if
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* the semaphore was negative (== somebody was waiting on it).
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* The default case (no contention) will result in NO
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* jumps for both down() and up().
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*/
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static inline void up(struct semaphore *sem)
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{
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register struct semaphore *sem1 __asm__ ("%a1") = sem;
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__asm__ __volatile__(
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"| atomic up operation\n\t"
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"addql #1,%0@\n\t"
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"jle 2f\n"
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"1:\n"
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LOCK_SECTION_START(".even\n\t")
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"2:\t"
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"pea 1b\n\t"
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"jbra __up_wakeup\n"
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LOCK_SECTION_END
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: /* no outputs */
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: "a" (sem1)
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: "memory");
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}
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#endif /* __ASSEMBLY__ */
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#endif
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#include <linux/semaphore.h>
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