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(), pthread_mutex_destroy(), pthread_mutex_lock()

       The Base Definitions volume of POSIX.1‐2017, <pthread.h>

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 .