1PTHREAD_RWLOCK_UNLOCK(P)   POSIX Programmer's Manual  PTHREAD_RWLOCK_UNLOCK(P)
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NAME

6       pthread_rwlock_unlock - unlock a read-write lock object
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SYNOPSIS

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

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

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

48       The pthread_rwlock_unlock() function may fail if:
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50       EINVAL The value specified by rwlock does not refer to  an  initialized
51              read-write lock object.
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53       EPERM  The current thread does not hold a lock on the read-write lock.
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56       The  pthread_rwlock_unlock() function shall not return an error code of
57       [EINTR].
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59       The following sections are informative.
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EXAMPLES

62       None.
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APPLICATION USAGE

65       None.
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RATIONALE

68       None.
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FUTURE DIRECTIONS

71       None.
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SEE ALSO

74       pthread_rwlock_destroy()       ,       pthread_rwlock_rdlock()        ,
75       pthread_rwlock_timedrdlock()     ,    pthread_rwlock_timedwrlock()    ,
76       pthread_rwlock_tryrdlock()     ,      pthread_rwlock_trywrlock()      ,
77       pthread_rwlock_wrlock()    ,    the    Base   Definitions   volume   of
78       IEEE Std 1003.1-2001, <pthread.h>
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81       Portions of this text are reprinted and reproduced in  electronic  form
82       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
83       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
84       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
85       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
86       event of any discrepancy between this version and the original IEEE and
87       The Open Group Standard, the original IEEE and The Open Group  Standard
88       is  the  referee document. The original Standard can be obtained online
89       at http://www.opengroup.org/unix/online.html .
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93IEEE/The Open Group                  2003             PTHREAD_RWLOCK_UNLOCK(P)
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