1PTHREAD_RWLOCK_UNLOCK(3P)  POSIX Programmer's Manual PTHREAD_RWLOCK_UNLOCK(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

13       pthread_rwlock_unlock — unlock a read-write lock object
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SYNOPSIS

16       #include <pthread.h>
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18       int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
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DESCRIPTION

21       The pthread_rwlock_unlock() function shall release a lock held  on  the
22       read-write  lock object referenced by rwlock.  Results are undefined if
23       the read-write lock rwlock is not held by the calling thread.
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25       If this function is called to release a read lock from  the  read-write
26       lock object and there are other read locks currently held on this read-
27       write lock object, the read-write  lock  object  remains  in  the  read
28       locked  state.  If  this  function releases the last read lock for this
29       read-write lock object, the read-write lock object shall be put in  the
30       unlocked state with no owners.
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32       If  this function is called to release a write lock for this read-write
33       lock object, the read-write lock object shall be put  in  the  unlocked
34       state.
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36       If there are threads blocked on the lock when it becomes available, the
37       scheduling policy shall determine which  thread(s)  shall  acquire  the
38       lock.   If  the  Thread  Execution Scheduling option is supported, when
39       threads executing with the scheduling policies SCHED_FIFO, SCHED_RR, or
40       SCHED_SPORADIC  are waiting on the lock, they shall acquire the lock in
41       priority order when the lock  becomes  available.  For  equal  priority
42       threads,  write  locks  shall  take precedence over read locks.  If the
43       Thread Execution Scheduling option is not supported, it is  implementa‐
44       tion-defined whether write locks take precedence over read locks.
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46       Results  are undefined if this function is called with an uninitialized
47       read-write lock.
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RETURN VALUE

50       If successful, the pthread_rwlock_unlock() function shall return  zero;
51       otherwise, an error number shall be returned to indicate the error.
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ERRORS

54       The  pthread_rwlock_unlock() function shall not return an error code of
55       [EINTR].
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57       The following sections are informative.
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EXAMPLES

60       None.
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APPLICATION USAGE

63       None.
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RATIONALE

66       If an implementation detects that the value  specified  by  the  rwlock
67       argument  to  pthread_rwlock_unlock()  does not refer to an initialized
68       read-write lock object, it is recommended that the function should fail
69       and report an [EINVAL] error.
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71       If  an  implementation  detects  that the value specified by the rwlock
72       argument to pthread_rwlock_unlock() refers to a read-write lock  object
73       for  which  the  current thread does not hold a lock, it is recommended
74       that the function should fail and report an [EPERM] error.
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FUTURE DIRECTIONS

77       None.
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SEE ALSO

80       pthread_rwlock_destroy(), pthread_rwlock_rdlock(), pthread_rwlock_time‐
81       drdlock(), pthread_rwlock_timedwrlock(), pthread_rwlock_trywrlock()
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83       The  Base Definitions volume of POSIX.1‐2008, Section 4.11, Memory Syn‐
84       chronization, <pthread.h>
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87       Portions of this text are reprinted and reproduced in  electronic  form
88       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
89       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
90       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
91       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
92       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
93       event of any discrepancy between this version and the original IEEE and
94       The  Open Group Standard, the original IEEE and The Open Group Standard
95       is the referee document. The original Standard can be  obtained  online
96       at http://www.unix.org/online.html .
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98       Any  typographical  or  formatting  errors that appear in this page are
99       most likely to have been introduced during the conversion of the source
100       files  to  man page format. To report such errors, see https://www.ker‐
101       nel.org/doc/man-pages/reporting_bugs.html .
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105IEEE/The Open Group                  2013            PTHREAD_RWLOCK_UNLOCK(3P)
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