PTHREAD_RWLOCK_TIMEDRDLOCK(POSIX Programmer's MaPTHREAD_RWLOCK_TIMEDRDLOCK(3P)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.
NAMEpthread_rwlock_timedrdlock — lock a read-write lock for reading
int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rwlock,
const struct timespec *restrict abstime);
The pthread_rwlock_timedrdlock() function shall apply a read lock to
the read-write lock referenced by rwlock as in the
pthread_rwlock_rdlock() function. However, if the lock cannot be
acquired without waiting for other threads to unlock the lock, this
wait shall be terminated when the specified timeout expires. The time‐
out shall expire when the absolute time specified by abstime passes, as
measured by the clock on which timeouts are based (that is, when the
value of that clock equals or exceeds abstime), or if the absolute time
specified by abstime has already been passed at the time of the call.
The timeout shall be based on the CLOCK_REALTIME clock. The resolution
of the timeout shall be the resolution of the CLOCK_REALTIME clock. The
timespec data type is defined in the <time.h> header. Under no circum‐
stances shall the function fail with a timeout if the lock can be
acquired immediately. The validity of the abstime parameter need not be
checked if the lock can be immediately acquired.
If a signal that causes a signal handler to be executed is delivered to
a thread blocked on a read-write lock via a call to
pthread_rwlock_timedrdlock(), upon return from the signal handler the
thread shall resume waiting for the lock as if it was not interrupted.
The calling thread may deadlock if at the time the call is made it
holds a write lock on rwlock. The results are undefined if this func‐
tion is called with an uninitialized read-write lock.
The pthread_rwlock_timedrdlock() function shall return zero if the lock
for reading on the read-write lock object referenced by rwlock is
acquired. Otherwise, an error number shall be returned to indicate the
The pthread_rwlock_timedrdlock() function shall fail if:
The lock could not be acquired before the specified timeout
The pthread_rwlock_timedrdlock() function may fail if:
EAGAIN The read lock could not be acquired because the maximum number
of read locks for lock would be exceeded.
A deadlock condition was detected or the calling thread already
holds a write lock on rwlock.
EINVAL The abstime nanosecond value is less than zero or greater than
or equal to 1000 million.
This function shall not return an error code of [EINTR].
The following sections are informative.
Applications using this function may be subject to priority inversion,
as discussed in the Base Definitions volume of POSIX.1‐2008, Section
3.287, Priority Inversion.
If an implementation detects that the value specified by the rwlock
argument to pthread_rwlock_timedrdlock() does not refer to an initial‐
ized read-write lock object, it is recommended that the function should
fail and report an [EINVAL] error.
SEE ALSOpthread_rwlock_destroy(), pthread_rwlock_rdlock(),
The Base Definitions volume of POSIX.1‐2008, Section 3.287, Priority
Inversion, Section 4.11, Memory Synchronization, <pthread.h>, <time.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
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