Originální popis anglicky:
sem_timedwait - lock a semaphore (
ADVANCED REALTIME)
Návod, kniha: POSIX Programmer's Manual
#include <semaphore.h>
#include <time.h>
int sem_timedwait(sem_t *restrict
sem,
const struct timespec *restrict
abs_timeout);
The
sem_timedwait() function shall lock the semaphore referenced by
sem as in the
sem_wait() function. However, if the semaphore
cannot be locked without waiting for another process or thread to unlock the
semaphore by performing a
sem_post() function, this wait shall be
terminated when the specified timeout expires.
The timeout shall expire when the absolute time specified by
abs_timeout
passes, as measured by the clock on which timeouts are based (that is, when
the value of that clock equals or exceeds
abs_timeout), or if the
absolute time specified by
abs_timeout has already been passed at the
time of the call.
If the Timers option is supported, the timeout shall be based on the
CLOCK_REALTIME clock. If the Timers option is not supported, the timeout shall
be based on the system clock as returned by the
time() function. The
resolution of the timeout shall be the resolution of the clock on which it is
based. The
timespec data type is defined as a structure in the
<time.h> header.
Under no circumstance shall the function fail with a timeout if the semaphore
can be locked immediately. The validity of the
abs_timeout need not be
checked if the semaphore can be locked immediately.
The
sem_timedwait() function 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_timedwait() function shall fail if:
- EINVAL
- The sem argument does not refer to a valid
semaphore.
- EINVAL
- The process or thread would have blocked, and the
abs_timeout parameter specified a nanoseconds field value less than
zero or greater than or equal to 1000 million.
- ETIMEDOUT
- The semaphore could not be locked before the specified
timeout expired.
The
sem_timedwait() function may fail if:
- EDEADLK
- A deadlock condition was detected.
- EINTR
- A signal interrupted this function.
The following sections are informative.
None.
Applications using these functions may be subject to priority inversion, as
discussed in the Base Definitions volume of
IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.
The
sem_timedwait() function is part of the Semaphores and Timeouts
options and need not be provided on all implementations.
None.
None.
sem_post() ,
sem_trywait() ,
sem_wait() ,
semctl() ,
semget() ,
semop() ,
time() , the Base Definitions volume
of IEEE Std 1003.1-2001,
<semaphore.h>,
<time.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 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
.
