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#ifndef _I386_SEMAPHORE_H
#define _I386_SEMAPHORE_H
#include <linux/linkage.h>
/*
* SMP- and interrupt-safe semaphores..
*
* (C) Copyright 1996 Linus Torvalds
*
* Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in
* the original code and to make semaphore waits
* interruptible so that processes waiting on
* semaphores can be killed.
*
* If you would like to see an analysis of this implementation, please
* ftp to gcom.com and download the file
* /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
*
*/
#include <asm/system.h>
#include <asm/atomic.h>
struct semaphore {
atomic_t count;
int waking;
struct wait_queue * wait;
};
#define MUTEX ((struct semaphore) { ATOMIC_INIT(1), 0, NULL })
#define MUTEX_LOCKED ((struct semaphore) { ATOMIC_INIT(0), 0, NULL })
asmlinkage void __down_failed(void /* special register calling convention */);
asmlinkage int __down_failed_interruptible(void /* params in registers */);
asmlinkage void __up_wakeup(void /* special register calling convention */);
extern void __down(struct semaphore * sem);
extern void __up(struct semaphore * sem);
#define sema_init(sem, val) atomic_set(&((sem)->count), (val))
/*
* These two _must_ execute atomically wrt each other.
*
* This is trivially done with load_locked/store_cond,
* but on the x86 we need an external synchronizer.
* Currently this is just the global interrupt lock,
* bah. Go for a smaller spinlock some day.
*
* (On the other hand this shouldn't be in any critical
* path, so..)
*/
static inline void wake_one_more(struct semaphore * sem)
{
unsigned long flags;
save_flags(flags);
cli();
sem->waking++;
restore_flags(flags);
}
static inline int waking_non_zero(struct semaphore *sem)
{
unsigned long flags;
int ret = 0;
save_flags(flags);
cli();
if (sem->waking > 0) {
sem->waking--;
ret = 1;
}
restore_flags(flags);
return ret;
}
/*
* This is ugly, but we want the default case to fall through.
* "down_failed" is a special asm handler that calls the C
* routine that actually waits. See arch/i386/lib/semaphore.S
*/
extern inline void down(struct semaphore * sem)
{
__asm__ __volatile__(
"# atomic down operation\n\t"
#ifdef __SMP__
"lock ; "
#endif
"decl 0(%0)\n\t"
"js 2f\n"
"1:\n"
".section .text.lock,\"ax\"\n"
"2:\tpushl $1b\n\t"
"jmp __down_failed\n"
".previous"
:/* no outputs */
:"c" (sem)
:"memory");
}
extern inline int down_interruptible(struct semaphore * sem)
{
int result;
__asm__ __volatile__(
"# atomic interruptible down operation\n\t"
#ifdef __SMP__
"lock ; "
#endif
"decl 0(%1)\n\t"
"js 2f\n\t"
"xorl %0,%0\n"
"1:\n"
".section .text.lock,\"ax\"\n"
"2:\tpushl $1b\n\t"
"jmp __down_failed_interruptible\n"
".previous"
:"=a" (result)
:"c" (sem)
:"memory");
return result;
}
/*
* Note! This is subtle. We jump to wake people up only if
* the semaphore was negative (== somebody was waiting on it).
* The default case (no contention) will result in NO
* jumps for both down() and up().
*/
extern inline void up(struct semaphore * sem)
{
__asm__ __volatile__(
"# atomic up operation\n\t"
#ifdef __SMP__
"lock ; "
#endif
"incl 0(%0)\n\t"
"jle 2f\n"
"1:\n"
".section .text.lock,\"ax\"\n"
"2:\tpushl $1b\n\t"
"jmp __up_wakeup\n"
".previous"
:/* no outputs */
:"c" (sem)
:"memory");
}
#endif
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