|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
|
|
|
SEM_TRYWAIT(3P) POSIX Programmer's Manual SEM_TRYWAIT(3P)
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.
sem_trywait, sem_wait — lock a semaphore
#include <semaphore.h>
int sem_trywait(sem_t *sem);
int sem_wait(sem_t *sem);
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.
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.
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.
None.
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.
None.
None.
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)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any
discrepancy between this version and the original IEEE and The
Open Group Standard, the original IEEE and The Open Group
Standard is the referee document. The original Standard can be
obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 SEM_TRYWAIT(3P)
Pages that refer to this page: semaphore.h(0p), semctl(3p), semget(3p), sem_getvalue(3p), sem_init(3p), semop(3p), sem_open(3p), sem_post(3p), sem_timedwait(3p), sem_wait(3p)
|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|