# pthread_mutexattr_getrobust

## 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.
    


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