Manpages - pthread_mutexattr_getrobust.3p

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.

pthread_mutexattr_getrobust, pthread_mutexattr_setrobust — get and set the mutex robust attribute

  #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);

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.

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.

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.

None.

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.

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.

None.

/pthread_mutex_consistent ( )/, /pthread_mutex_destroy ( )/, /pthread_mutex_lock ( )/

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

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 .

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