85 lines
3.1 KiB
Groff
85 lines
3.1 KiB
Groff
.TH PTHREAD_MUTEXATTR 3 LinuxThreads
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.XREF pthread_mutexattr_destroy
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.XREF pthread_mutexattr_setkind_np
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.XREF pthread_mutexattr_getkind_np
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.SH NAME
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pthread_mutexattr_init, pthread_mutexattr_destroy, pthread_mutexattr_setkind_np, pthread_mutexattr_getkind_np \- mutex creation attributes
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.SH SYNOPSIS
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#include <pthread.h>
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int pthread_mutexattr_init(pthread_mutexattr_t *attr);
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int pthread_mutexattr_destroy(pthread_mutexattr_t *attr);
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int pthread_mutexattr_setkind_np(pthread_mutexattr_t *attr, int kind);
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int pthread_mutexattr_getkind_np(const pthread_mutexattr_t *attr, int *kind);
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.SH DESCRIPTION
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Mutex attributes can be specified at mutex creation time, by passing a
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mutex attribute object as second argument to !pthread_mutex_init!(3).
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Passing !NULL! is equivalent to passing a mutex attribute object with
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all attributes set to their default values.
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!pthread_mutexattr_init! initializes the mutex attribute object |attr|
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and fills it with default values for the attributes.
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!pthread_mutexattr_destroy! destroys a mutex attribute object, which
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must not be reused until it is reinitialized. !pthread_mutexattr_destroy!
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does nothing in the LinuxThreads implementation.
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LinuxThreads supports only one mutex attribute: the mutex kind, which
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is either !PTHREAD_MUTEX_FAST_NP! for ``fast'' mutexes,
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!PTHREAD_MUTEX_RECURSIVE_NP! for ``recursive'' mutexes,
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or !PTHREAD_MUTEX_ERRORCHECK_NP! for ``error checking'' mutexes.
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As the !NP! suffix indicates, this is a non-portable extension to the
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POSIX standard and should not be employed in portable programs.
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The mutex kind determines what happens if a thread attempts to lock a
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mutex it already owns with !pthread_mutex_lock!(3). If the mutex is of
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the ``fast'' kind, !pthread_mutex_lock!(3) simply suspends the calling
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thread forever. If the mutex is of the ``error checking'' kind,
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!pthread_mutex_lock!(3) returns immediately with the error code
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!EDEADLK!. If the mutex is of the ``recursive'' kind, the call to
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!pthread_mutex_lock!(3) returns immediately with a success return
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code. The number of times the thread owning the mutex has locked it is
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recorded in the mutex. The owning thread must call
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!pthread_mutex_unlock!(3) the same number of times before the mutex
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returns to the unlocked state.
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The default mutex kind is ``fast'', that is, !PTHREAD_MUTEX_FAST_NP!.
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!pthread_mutexattr_setkind_np! sets the mutex kind attribute in |attr|
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to the value specified by |kind|.
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!pthread_mutexattr_getkind_np! retrieves the current value of the
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mutex kind attribute in |attr| and stores it in the location pointed
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to by |kind|.
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.SH "RETURN VALUE"
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!pthread_mutexattr_init!, !pthread_mutexattr_destroy! and
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!pthread_mutexattr_getkind_np! always return 0.
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!pthread_mutexattr_setkind_np! returns 0 on success and a non-zero
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error code on error.
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.SH ERRORS
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On error, !pthread_mutexattr_setkind_np! returns the following error code:
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.TP
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!EINVAL!
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|kind| is neither !PTHREAD_MUTEX_FAST_NP! nor !PTHREAD_MUTEX_RECURSIVE_NP!
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nor !PTHREAD_MUTEX_ERRORCHECK_NP!
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.SH AUTHOR
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Xavier Leroy <Xavier.Leroy@inria.fr>
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.SH "SEE ALSO"
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!pthread_mutex_init!(3),
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!pthread_mutex_lock!(3),
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!pthread_mutex_unlock!(3).
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