forked from mirrors/linux
48380368de
Fundamentally semaphores are a counted primitive, but DEFINE_SEMAPHORE() does not expose this and explicitly creates a binary semaphore. Change DEFINE_SEMAPHORE() to take a number argument and use that in the few places that open-coded it using __SEMAPHORE_INITIALIZER(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> [mcgrof: add some tribal knowledge about why some folks prefer binary sempahores over mutexes] Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
51 lines
1.6 KiB
C
51 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (c) 2008 Intel Corporation
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* Author: Matthew Wilcox <willy@linux.intel.com>
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*
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* Please see kernel/locking/semaphore.c for documentation of these functions
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*/
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#ifndef __LINUX_SEMAPHORE_H
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#define __LINUX_SEMAPHORE_H
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#include <linux/list.h>
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#include <linux/spinlock.h>
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/* Please don't access any members of this structure directly */
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struct semaphore {
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raw_spinlock_t lock;
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unsigned int count;
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struct list_head wait_list;
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};
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#define __SEMAPHORE_INITIALIZER(name, n) \
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{ \
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.lock = __RAW_SPIN_LOCK_UNLOCKED((name).lock), \
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.count = n, \
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.wait_list = LIST_HEAD_INIT((name).wait_list), \
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}
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/*
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* Unlike mutexes, binary semaphores do not have an owner, so up() can
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* be called in a different thread from the one which called down().
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* It is also safe to call down_trylock() and up() from interrupt
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* context.
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*/
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#define DEFINE_SEMAPHORE(_name, _n) \
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struct semaphore _name = __SEMAPHORE_INITIALIZER(_name, _n)
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static inline void sema_init(struct semaphore *sem, int val)
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{
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static struct lock_class_key __key;
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*sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
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lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0);
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}
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extern void down(struct semaphore *sem);
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extern int __must_check down_interruptible(struct semaphore *sem);
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extern int __must_check down_killable(struct semaphore *sem);
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extern int __must_check down_trylock(struct semaphore *sem);
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extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
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extern void up(struct semaphore *sem);
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#endif /* __LINUX_SEMAPHORE_H */
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