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.
pthread_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 timeout 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 circumstances 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
function 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 error.
The pthread_rwlock_timedrdlock() function shall fail if:
- The lock could not be acquired before the specified timeout expired.
The pthread_rwlock_timedrdlock() function may fail if:
- 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.
- 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
The following sections are informative.
Applications using this function may be subject to priority inversion, as
discussed in the Base Definitions volume of POSIX.1‐2017, Section
3.291, Priority Inversion.
If an implementation detects that the value specified by the rwlock
argument to pthread_rwlock_timedrdlock() does not refer to an
initialized read-write lock object, it is recommended that the function should
fail and report an [EINVAL] error.
The Base Definitions volume of POSIX.1‐2017, Section
3.291, Priority Inversion, Section 4.12, Memory
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 .
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