PTHREAD_MUTEXATTR_GETROBUST(P3O)SIX Programmer's ManPuTaHlREAD_MUTEXATTR_GETROBUST(3)



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

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 .



IEEE/The Open Group                  2017       PTHREAD_MUTEXATTR_GETROBUST(3)
