pthread_mutexattr_getrobust(3p) — Linux manual page

PTHREAD...ETROBUST(3P)  POSIX Programmer's Manual PTHREAD...ETROBUST(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.

NAME

       pthread_mutexattr_getrobust, pthread_mutexattr_setrobust — get
       and set the mutex robust attribute

SYNOPSIS

       #include <pthread.h>

       int pthread_mutexattr_getrobust(const pthread_mutexattr_t *restrict
           attr, int *restrict robust);
       int pthread_mutexattr_setrobust(pthread_mutexattr_t *attr,
           int robust);

DESCRIPTION

       The pthread_mutexattr_getrobust() and
       pthread_mutexattr_setrobust() functions, respectively, shall get
       and set the mutex robust attribute. This attribute is set in the
       robust parameter. Valid values for robust include:

       PTHREAD_MUTEX_STALLED
             No special actions are taken if the owner of the mutex is
             terminated while holding the mutex lock. This can lead to
             deadlocks if no other thread can unlock the mutex.
             This is the default value.

       PTHREAD_MUTEX_ROBUST
             If the process containing the owning thread of a robust
             mutex terminates while holding the mutex lock, the next
             thread that acquires the mutex shall be notified about the
             termination by the return value [EOWNERDEAD] from the
             locking function. If the owning thread of a robust mutex
             terminates while holding the mutex lock, the next thread
             that attempts to acquire the mutex may be notified about
             the termination by the return value [EOWNERDEAD].  The
             notified thread can then attempt to make the state
             protected by the mutex consistent again, and if successful
             can mark the mutex state as consistent by calling
             pthread_mutex_consistent().  After a subsequent successful
             call to pthread_mutex_unlock(), the mutex lock shall be
             released and can be used normally by other threads. If the
             mutex is unlocked without a call to
             pthread_mutex_consistent(), it shall be in a permanently
             unusable state and all attempts to lock the mutex shall
             fail with the error [ENOTRECOVERABLE].  The only
             permissible operation on such a mutex is
             pthread_mutex_destroy().

       The behavior is undefined if the value specified by the attr
       argument to pthread_mutexattr_getrobust() or
       pthread_mutexattr_setrobust() does not refer to an initialized
       mutex attributes object.

RETURN VALUE

       Upon successful completion, the pthread_mutexattr_getrobust()
       function shall return zero and store the value of the robust
       attribute of attr into the object referenced by the robust
       parameter. Otherwise, an error value shall be returned to
       indicate the error. If successful, the
       pthread_mutexattr_setrobust() function shall return zero;
       otherwise, an error number shall be returned to indicate the
       error.

ERRORS

       The pthread_mutexattr_setrobust() function shall fail if:

       EINVAL The value of robust is invalid.

       These functions shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       The actions required to make the state protected by the mutex
       consistent again are solely dependent on the application. If it
       is not possible to make the state of a mutex consistent, robust
       mutexes can be used to notify this situation by calling
       pthread_mutex_unlock() without a prior call to
       pthread_mutex_consistent().

       If the state is declared inconsistent by calling
       pthread_mutex_unlock() without a prior call to
       pthread_mutex_consistent(), a possible approach could be to
       destroy the mutex and then reinitialize it. However, it should be
       noted that this is possible only in certain situations where the
       state protected by the mutex has to be reinitialized and
       coordination achieved with other threads blocked on the mutex,
       because otherwise a call to a locking function with a reference
       to a mutex object invalidated by a call to
       pthread_mutex_destroy() results in undefined behavior.

RATIONALE

       If an implementation detects that the value specified by the attr
       argument to pthread_mutexattr_getrobust() or
       pthread_mutexattr_setrobust() does not refer to an initialized
       mutex attributes object, it is recommended that the function
       should fail and report an [EINVAL] error.

FUTURE DIRECTIONS

       None.

SEE ALSO

       pthread_mutex_consistent(3p), pthread_mutex_destroy(3p),
       pthread_mutex_lock(3p)

       The Base Definitions volume of POSIX.1‐2017, pthread.h(0p)

COPYRIGHT

       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 .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017            PTHREAD...ETROBUST(3P)

Pages that refer to this page: pthread.h(0p), pthread_mutexattr_setrobust(3p), pthread_mutex_consistent(3p), pthread_mutex_destroy(3p), pthread_mutex_lock(3p)

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