include/linux/semaphore.h

Source file repositories/reference/linux-study-clean/include/linux/semaphore.h

File Facts

System
Linux kernel
Corpus path
include/linux/semaphore.h
Extension
.h
Size
1953 bytes
Lines
65
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct semaphore {
	raw_spinlock_t		lock;
	unsigned int		count;
	struct semaphore_waiter *first_waiter;

#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
	unsigned long		last_holder;
#endif
};

#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
#define __LAST_HOLDER_SEMAPHORE_INITIALIZER				\
	, .last_holder = 0UL
#else
#define __LAST_HOLDER_SEMAPHORE_INITIALIZER
#endif

#define __SEMAPHORE_INITIALIZER(name, n)				\
{									\
	.lock		= __RAW_SPIN_LOCK_UNLOCKED((name).lock),	\
	.count		= n,						\
	.first_waiter	= NULL						\
	__LAST_HOLDER_SEMAPHORE_INITIALIZER				\
}

/*
 * Unlike mutexes, binary semaphores do not have an owner, so up() can
 * be called in a different thread from the one which called down().
 * It is also safe to call down_trylock() and up() from interrupt
 * context.
 */
#define DEFINE_SEMAPHORE(_name, _n)	\
	struct semaphore _name = __SEMAPHORE_INITIALIZER(_name, _n)

static inline void sema_init(struct semaphore *sem, int val)
{
	static struct lock_class_key __key;
	*sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
	lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0);
}

extern void down(struct semaphore *sem);
extern int __must_check down_interruptible(struct semaphore *sem);
extern int __must_check down_killable(struct semaphore *sem);
extern int __must_check down_trylock(struct semaphore *sem);
extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
extern void up(struct semaphore *sem);
extern unsigned long sem_last_holder(struct semaphore *sem);

#endif /* __LINUX_SEMAPHORE_H */

Annotation

Implementation Notes