diff options
Diffstat (limited to 'include/asm-i386/semaphore.h')
| -rw-r--r-- | include/asm-i386/semaphore.h | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/include/asm-i386/semaphore.h b/include/asm-i386/semaphore.h new file mode 100644 index 000000000000..ea563da63e24 --- /dev/null +++ b/include/asm-i386/semaphore.h @@ -0,0 +1,194 @@ +#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 __MUTEX_INITIALIZER(name) \ + __SEMAPHORE_INITIALIZER(name,1) + +#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 "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 "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 "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 "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 |