PTHREAD_MUTEXATTR_GETROBUSTPOSIX Programmer's MPTHREAD_MUTEXATTR_GETROBUST(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 termi‐
nated 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 own‐
ing thread of a robust mutex terminates while holding the mutex
lock, the next thread that acquires the mutex may be notified
about the termination by the return value [EOWNERDEAD]. The
notified thread can then attempt to mark the state protected by
the mutex as consistent again by a call to pthread_mutex_consis‐
tent(). 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 with‐
out a call to pthread_mutex_consistent(), it shall be in a perma‐
nently 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 consis‐
tent again are solely dependent on the application. If it is not possi‐
ble 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 coordina‐
tion achieved with other threads blocked on the mutex, because other‐
wise 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 argu‐
ment to pthread_mutexattr_getrobust() or pthread_mutexattr_setrobust()
does not refer to an initialized mutex attributes object, it is recom‐
mended that the function should fail and report an [EINVAL] error.
FUTURE DIRECTIONS
None.
SEE ALSOpthread_mutex_consistent(), pthread_mutex_destroy(),
pthread_mutex_lock()
The Base Definitions volume of POSIX.1‐2008, <pthread.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 PTHREAD_MUTEXATTR_GETROBUST(3P)
