заблокировать семафор (lock a semaphore)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
sem_trywait, sem_wait — lock a semaphore
Синопсис (Synopsis)
#include <semaphore.h>
int sem_trywait(sem_t *sem);
int sem_wait(sem_t *sem);
Описание (Description)
The sem_trywait() function shall lock the semaphore referenced by
sem only if the semaphore is currently not locked; that is, if
the semaphore value is currently positive. Otherwise, it shall
not lock the semaphore.
The sem_wait() function shall lock the semaphore referenced by
sem by performing a semaphore lock operation on that semaphore.
If the semaphore value is currently zero, then the calling thread
shall not return from the call to sem_wait() until it either
locks the semaphore or the call is interrupted by a signal.
Upon successful return, the state of the semaphore shall be
locked and shall remain locked until the sem_post() function is
executed and returns successfully.
The sem_wait() function is interruptible by the delivery of a
signal.
Возвращаемое значение (Return value)
The sem_trywait() and sem_wait() functions shall return zero if
the calling process successfully performed the semaphore lock
operation on the semaphore designated by sem. If the call was
unsuccessful, the state of the semaphore shall be unchanged, and
the function shall return a value of -1 and set errno to indicate
the error.
Ошибки (Error)
The sem_trywait() function shall fail if:
EAGAIN The semaphore was already locked, so it cannot be
immediately locked by the sem_trywait() operation.
The sem_trywait() and sem_wait() functions may fail if:
EDEADLK
A deadlock condition was detected.
EINTR A signal interrupted this function.
EINVAL The sem argument does not refer to a valid semaphore.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
Applications using these functions may be subject to priority
inversion, as discussed in the Base Definitions volume of
POSIX.1‐2017, Section 3.291, Priority Inversion.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
semctl(3p), semget(3p), semop(3p), sem_post(3p),
sem_timedwait(3p)
The Base Definitions volume of POSIX.1‐2017, Section 3.291,
Priority Inversion, Section 4.12, Memory Synchronization,
semaphore.h(0p)
