/* * include/asm-s390/semaphore.h * * S390 version * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation * * Derived from "include/asm-i386/semaphore.h" * (C) Copyright 1996 Linus Torvalds */ #ifndef _S390_SEMAPHORE_H #define _S390_SEMAPHORE_H #include <asm/system.h> #include <asm/atomic.h> #include <linux/wait.h> #include <linux/rwsem.h> struct semaphore { /* * Note that any negative value of count is equivalent to 0, * but additionally indicates that some process(es) might be * sleeping on `wait'. */ atomic_t count; wait_queue_head_t wait; }; #define __SEMAPHORE_INITIALIZER(name,count) \ { ATOMIC_INIT(count), __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) { atomic_set(&sem->count, val); 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); } 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); static inline void down(struct semaphore * sem) { might_sleep(); if (atomic_dec_return(&sem->count) < 0) __down(sem); } static inline int down_interruptible(struct semaphore * sem) { int ret = 0; might_sleep(); if (atomic_dec_return(&sem->count) < 0) ret = __down_interruptible(sem); return ret; } static inline int down_trylock(struct semaphore * sem) { int old_val, new_val; /* * This inline assembly atomically implements the equivalent * to the following C code: * old_val = sem->count.counter; * if ((new_val = old_val) > 0) * sem->count.counter = --new_val; * In the ppc code this is called atomic_dec_if_positive. */ asm volatile( " l %0,0(%3)\n" "0: ltr %1,%0\n" " jle 1f\n" " ahi %1,-1\n" " cs %0,%1,0(%3)\n" " jl 0b\n" "1:" : "=&d" (old_val), "=&d" (new_val), "=m" (sem->count.counter) : "a" (&sem->count.counter), "m" (sem->count.counter) : "cc", "memory"); return old_val <= 0; } static inline void up(struct semaphore * sem) { if (atomic_inc_return(&sem->count) <= 0) __up(sem); } #endif