[deliverable/linux.git] / include / asm-i386 / semaphore.h

#ifndef _I386_SEMAPHORE_H
#define _I386_SEMAPHORE_H

#include <linux/linkage.h>

#ifdef __KERNEL__

/*
 * 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.
 * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper
 *		       functions in asm/sempahore-helper.h while fixing a
 *		       potential and subtle race discovered by Ulrich Schmid
 *		       in down_interruptible(). Since I started to play here I
 *		       also implemented the `trylock' semaphore operation.
 *          1999-07-02 Artur Skawina <skawina@geocities.com>
 *                     Optimized "0(ecx)" -> "(ecx)" (the assembler does not
 *                     do this). Changed calling sequences from push/jmp to
 *                     traditional call/ret.
 * Modified 2001-01-01 Andreas Franck <afranck@gmx.de>
 *		       Some hacks to ensure compatibility with recent
 *		       GCC snapshots, to avoid stack corruption when compiling
 *		       with -fomit-frame-pointer. It's not sure if this will
 *		       be fixed in GCC, as our previous implementation was a
 *		       bit dubious.
 *
 * 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>
#include <linux/wait.h>
#include <linux/rwsem.h>

struct semaphore {
	atomic_t count;
	int sleepers;
	wait_queue_head_t wait;
};


#define __SEMAPHORE_INITIALIZER(name, n)				\
{									\
	.count		= ATOMIC_INIT(n),				\
	.sleepers	= 0,						\
	.wait		= __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)	\
}

#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)

#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)

static inline void sema_init (struct semaphore *sem, int val)
{
/*
 *	*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
 *
 * i'd rather use the more flexible initialization above, but sadly
 * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well.
 */
	atomic_set(&sem->count, val);
	sem->sleepers = 0;
	init_waitqueue_head(&sem->wait);
}

static inline void init_MUTEX (struct semaphore *sem)
{
	sema_init(sem, 1);
}

static inline void init_MUTEX_LOCKED (struct semaphore *sem)
{
	sema_init(sem, 0);
}

fastcall void __down_failed(void /* special register calling convention */);
fastcall int  __down_failed_interruptible(void  /* params in registers */);
fastcall int  __down_failed_trylock(void  /* params in registers */);
fastcall void __up_wakeup(void /* special register calling convention */);

/*
 * 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/kernel/semaphore.c
 */
static inline void down(struct semaphore * sem)
{
	might_sleep();
	__asm__ __volatile__(
		"# atomic down operation\n\t"
		LOCK_PREFIX "decl %0\n\t"     /* --sem->count */
		"js 2f\n"
		"1:\n"
		LOCK_SECTION_START("")
		"2:\tlea %0,%%eax\n\t"
		"call __down_failed\n\t"
		"jmp 1b\n"
		LOCK_SECTION_END
		:"+m" (sem->count)
		:
		:"memory","ax");
}

/*
 * Interruptible try to acquire a semaphore.  If we obtained
 * it, return zero.  If we were interrupted, returns -EINTR
 */
static inline int down_interruptible(struct semaphore * sem)
{
	int result;

	might_sleep();
	__asm__ __volatile__(
		"# atomic interruptible down operation\n\t"
		LOCK_PREFIX "decl %1\n\t"     /* --sem->count */
		"js 2f\n\t"
		"xorl %0,%0\n"
		"1:\n"
		LOCK_SECTION_START("")
		"2:\tlea %1,%%eax\n\t"
		"call __down_failed_interruptible\n\t"
		"jmp 1b\n"
		LOCK_SECTION_END
		:"=a" (result), "+m" (sem->count)
		:
		:"memory");
	return result;
}

/*
 * Non-blockingly attempt to down() a semaphore.
 * Returns zero if we acquired it
 */
static inline int down_trylock(struct semaphore * sem)
{
	int result;

	__asm__ __volatile__(
		"# atomic interruptible down operation\n\t"
		LOCK_PREFIX "decl %1\n\t"     /* --sem->count */
		"js 2f\n\t"
		"xorl %0,%0\n"
		"1:\n"
		LOCK_SECTION_START("")
		"2:\tlea %1,%%eax\n\t"
		"call __down_failed_trylock\n\t"
		"jmp 1b\n"
		LOCK_SECTION_END
		:"=a" (result), "+m" (sem->count)
		:
		:"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().
 */
static inline void up(struct semaphore * sem)
{
	__asm__ __volatile__(
		"# atomic up operation\n\t"
		LOCK_PREFIX "incl %0\n\t"     /* ++sem->count */
		"jle 2f\n"
		"1:\n"
		LOCK_SECTION_START("")
		"2:\tlea %0,%%eax\n\t"
		"call __up_wakeup\n\t"
		"jmp 1b\n"
		LOCK_SECTION_END
		".subsection 0\n"
		:"+m" (sem->count)
		:
		:"memory","ax");
}

#endif
#endif
Commit	Line	Data
1da177e4 LT	1	#ifndef _I386_SEMAPHORE_H
	2	#define _I386_SEMAPHORE_H
	3
	4	#include <linux/linkage.h>
	5
	6	#ifdef __KERNEL__
	7
	8	/*
	9	* SMP- and interrupt-safe semaphores..
	10	*
	11	* (C) Copyright 1996 Linus Torvalds
	12	*
	13	* Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in
	14	* the original code and to make semaphore waits
	15	* interruptible so that processes waiting on
	16	* semaphores can be killed.
	17	* Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper
	18	* functions in asm/sempahore-helper.h while fixing a
	19	* potential and subtle race discovered by Ulrich Schmid
	20	* in down_interruptible(). Since I started to play here I
	21	* also implemented the `trylock' semaphore operation.
	22	* 1999-07-02 Artur Skawina <skawina@geocities.com>
	23	* Optimized "0(ecx)" -> "(ecx)" (the assembler does not
	24	* do this). Changed calling sequences from push/jmp to
	25	* traditional call/ret.
	26	* Modified 2001-01-01 Andreas Franck <afranck@gmx.de>
	27	* Some hacks to ensure compatibility with recent
	28	* GCC snapshots, to avoid stack corruption when compiling
	29	* with -fomit-frame-pointer. It's not sure if this will
	30	* be fixed in GCC, as our previous implementation was a
	31	* bit dubious.
	32	*
	33	* If you would like to see an analysis of this implementation, please
	34	* ftp to gcom.com and download the file
	35	* /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
	36	*
	37	*/
	38
	39	#include <asm/system.h>
	40	#include <asm/atomic.h>
	41	#include <linux/wait.h>
	42	#include <linux/rwsem.h>
	43
	44	struct semaphore {
	45	atomic_t count;
	46	int sleepers;
	47	wait_queue_head_t wait;
	48	};
	49
	50
	51	#define __SEMAPHORE_INITIALIZER(name, n) \
	52	{ \
	53	.count = ATOMIC_INIT(n), \
	54	.sleepers = 0, \
	55	.wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
	56	}
	57
1da177e4 LT	58	#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
	59	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
	60
	61	#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
	62	#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
	63
	64	static inline void sema_init (struct semaphore *sem, int val)
	65	{
	66	/*
	67	* sem = (struct semaphore)__SEMAPHORE_INITIALIZER((sem),val);
	68	*
	69	* i'd rather use the more flexible initialization above, but sadly
	70	* GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well.
	71	*/
	72	atomic_set(&sem->count, val);
	73	sem->sleepers = 0;
	74	init_waitqueue_head(&sem->wait);
	75	}
	76
	77	static inline void init_MUTEX (struct semaphore *sem)
	78	{
	79	sema_init(sem, 1);
	80	}
	81
	82	static inline void init_MUTEX_LOCKED (struct semaphore *sem)
	83	{
	84	sema_init(sem, 0);
	85	}
	86
	87	fastcall void __down_failed(void /* special register calling convention */);
	88	fastcall int __down_failed_interruptible(void /* params in registers */);
	89	fastcall int __down_failed_trylock(void /* params in registers */);
	90	fastcall void __up_wakeup(void /* special register calling convention */);
	91
	92	/*
	93	* This is ugly, but we want the default case to fall through.
	94	* "__down_failed" is a special asm handler that calls the C
	95	* routine that actually waits. See arch/i386/kernel/semaphore.c
	96	*/
	97	static inline void down(struct semaphore * sem)
	98	{
	99	might_sleep();
	100	__asm__ __volatile__(
	101	"# atomic down operation\n\t"
9a0b5817	102	LOCK_PREFIX "decl %0\n\t" /* --sem->count */
1da177e4 LT	103	"js 2f\n"
	104	"1:\n"
	105	LOCK_SECTION_START("")
	106	"2:\tlea %0,%%eax\n\t"
	107	"call __down_failed\n\t"
	108	"jmp 1b\n"
	109	LOCK_SECTION_END
b862f3b0	110	:"+m" (sem->count)
1da177e4 LT	111	:
	112	:"memory","ax");
	113	}
	114
	115	/*
	116	* Interruptible try to acquire a semaphore. If we obtained
	117	* it, return zero. If we were interrupted, returns -EINTR
	118	*/
	119	static inline int down_interruptible(struct semaphore * sem)
	120	{
	121	int result;
	122
	123	might_sleep();
	124	__asm__ __volatile__(
	125	"# atomic interruptible down operation\n\t"
9a0b5817	126	LOCK_PREFIX "decl %1\n\t" /* --sem->count */
1da177e4 LT	127	"js 2f\n\t"
	128	"xorl %0,%0\n"
	129	"1:\n"
	130	LOCK_SECTION_START("")
	131	"2:\tlea %1,%%eax\n\t"
	132	"call __down_failed_interruptible\n\t"
	133	"jmp 1b\n"
	134	LOCK_SECTION_END
b862f3b0	135	:"=a" (result), "+m" (sem->count)
1da177e4 LT	136	:
	137	:"memory");
	138	return result;
	139	}
	140
	141	/*
	142	* Non-blockingly attempt to down() a semaphore.
	143	* Returns zero if we acquired it
	144	*/
	145	static inline int down_trylock(struct semaphore * sem)
	146	{
	147	int result;
	148
	149	__asm__ __volatile__(
	150	"# atomic interruptible down operation\n\t"
9a0b5817	151	LOCK_PREFIX "decl %1\n\t" /* --sem->count */
1da177e4 LT	152	"js 2f\n\t"
	153	"xorl %0,%0\n"
	154	"1:\n"
	155	LOCK_SECTION_START("")
	156	"2:\tlea %1,%%eax\n\t"
	157	"call __down_failed_trylock\n\t"
	158	"jmp 1b\n"
	159	LOCK_SECTION_END
b862f3b0	160	:"=a" (result), "+m" (sem->count)
1da177e4 LT	161	:
	162	:"memory");
	163	return result;
	164	}
	165
	166	/*
	167	* Note! This is subtle. We jump to wake people up only if
	168	* the semaphore was negative (== somebody was waiting on it).
	169	* The default case (no contention) will result in NO
	170	* jumps for both down() and up().
	171	*/
	172	static inline void up(struct semaphore * sem)
	173	{
	174	__asm__ __volatile__(
	175	"# atomic up operation\n\t"
9a0b5817	176	LOCK_PREFIX "incl %0\n\t" /* ++sem->count */
1da177e4 LT	177	"jle 2f\n"
	178	"1:\n"
	179	LOCK_SECTION_START("")
	180	"2:\tlea %0,%%eax\n\t"
	181	"call __up_wakeup\n\t"
	182	"jmp 1b\n"
	183	LOCK_SECTION_END
	184	".subsection 0\n"
b862f3b0	185	:"+m" (sem->count)
1da177e4 LT	186	:
	187	:"memory","ax");
	188	}
	189
	190	#endif
	191	#endif