new file 100644
/*
* Portions Copyright 2008 VMware, Inc.
*/
#ifndef _X86_64_SEMAPHORE_H
#define _X86_64_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 <asm/rwlock.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
#include <linux/stringify.h>
#if defined(__VMKLNX__)
#include "vmkapi.h"
#endif /* defined(__VMKLNX__) */
struct semaphore {
atomic_t count;
int sleepers;
wait_queue_head_t wait;
};
/**
* __SEMAPHORE_INITIALIZER - initialize the semaphore
* @name: name of the semaphore
* @n: count for the semaphore
* Initialize the semaphore and set its count to @n, the number of sleepers to
* 0 and initialize its wait queue.
* RETURN VALUE:
* This function does not return a value.
/* _VMKLNX_CODECHECK_: __SEMAPHORE_INITIALIZER */
#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)
* sema_init - Initializes semaphore value
* @sem: semaphore
* @val: value
* Initilizes semaphore value
* NONE
/* _VMKLNX_CODECHECK_: sema_init */
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);
* init_MUTEX - Initializes the semaphore as free resource with exclusive access.
* @sem: Pointer to semaphore
* The given semaphore is initialized as a free resource with exclusive
* access.
/* _VMKLNX_CODECHECK_: init_MUTEX */
static inline void init_MUTEX (struct semaphore *sem)
sema_init(sem, 1);
* init_MUTEX_LOCKED - Initializes the semaphore as busy resource with exclusive access.
* @sem: Pointer to semaphore.
* The given semaphore is initialized as a busy resource with exclusive access
* given to the caller of the initialization function.
/* _VMKLNX_CODECHECK_: init_MUTEX_LOCKED */
static inline void init_MUTEX_LOCKED (struct semaphore *sem)
sema_init(sem, 0);
asmlinkage void __down_failed(void /* special register calling convention */);
asmlinkage int __down_failed_interruptible(void /* params in registers */);
asmlinkage int __down_failed_trylock(void /* params in registers */);
asmlinkage void __up_wakeup(void /* special register calling convention */);
asmlinkage void __down(struct semaphore * sem);
asmlinkage int __down_interruptible(struct semaphore * sem);
asmlinkage int __down_trylock(struct semaphore * sem);
asmlinkage void __up(struct semaphore * sem);
* 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/x86_64/kernel/semaphore.c
* down - acquire a semaphore
* @sem: Pointer to the semaphore to be acquired
* Acquires the specified semaphore. If the semaphore's count of available
* acquisitions is exhausted, then the calling function will block.
* None
/* _VMKLNX_CODECHECK_: down */
static inline void down(struct semaphore * sem)
might_sleep();
vmk_AtomicPrologue();
__asm__ __volatile__(
"# atomic down operation\n\t"
LOCK_PREFIX "decl %0\n\t" /* --sem->count */
"js 2f\n"
"cmpb $0, vmk_AtomicUseFence(%%rip)\n"
"jne 4f\n"
"1:\n"
LOCK_SECTION_START("")
"2:\tcmpb $0, vmk_AtomicUseFence(%%rip)\n"
"jne 3f\n"
"call __down_failed\n\t"
"jmp 1b\n"
"3:\tlfence\n"
"4:\tlfence\n"
LOCK_SECTION_END
:"=m" (sem->count)
:"D" (sem)
:"memory");
#else /* !defined(__VMKLNX__) */
"2:\tcall __down_failed\n\t"
#endif /* !defined(__VMKLNX__) */
* Interruptible try to acquire a semaphore. If we obtained
* it, return zero. If we were interrupted, returns -EINTR
* down_interruptible - Acquire a semaphore with an interruptible wait
* Attempt to acquire the specified semaphore. If the semaphore's count of available
* acquisitions is exhausted, then the calling function will block. If a
* signal is received by the blocking thread, then this function aborts.
* 0 on successful acquisition, or -EINTR if interrupted by a signal
/* _VMKLNX_CODECHECK_: down_interruptible */
static inline int down_interruptible(struct semaphore * sem)
int result;
"# atomic interruptible down operation\n\t"
LOCK_PREFIX "decl %1\n\t" /* --sem->count */
"js 2f\n\t"
"xorl %0,%0\n"
"cmpb $0, vmk_AtomicUseFence(%%rip)\n\t"
"2:\tcmpb $0, vmk_AtomicUseFence(%%rip)\n\t"
"call __down_failed_interruptible\n\t"
:"=a" (result), "=m" (sem->count)
"2:\tcall __down_failed_interruptible\n\t"
return result;
* Non-blockingly attempt to down() a semaphore.
* Returns zero if we acquired it
* down_trylock - attempt to acquire a semaphore
* acquisitions is exhausted, then return immediately.
* 0 on successful acquisition, or 1 if the semaphore is not immediately available
/* _VMKLNX_CODECHECK_: down_trylock */
static inline int down_trylock(struct semaphore * sem)
"call __down_failed_trylock\n\t"
:"memory","cc");
"2:\tcall __down_failed_trylock\n\t"
* 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().
* up - release semaphore
* @sem: pointer to initialized and acquired semaphore
* none
/* _VMKLNX_CODECHECK_: up */
static inline void up(struct semaphore * sem)
"# atomic up operation\n\t"
LOCK_PREFIX "incl %0\n\t" /* ++sem->count */
"jle 2f\n"
"call __up_wakeup\n\t"
"2:\tcall __up_wakeup\n\t"
#endif /* __KERNEL__ */
#endif