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.TH PTHREAD_MUTEXATTR_GETROBUST "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH 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.

.SH NAME

pthread_mutexattr_getrobust,

pthread_mutexattr_setrobust

\(em get and set the mutex robust attribute

.SH SYNOPSIS

.LP

.nf

#include <pthread.h>

.P

int pthread_mutexattr_getrobust(const pthread_mutexattr_t *restrict

    \fIattr\fP, int *restrict \fIrobust\fP);

int pthread_mutexattr_setrobust(pthread_mutexattr_t *\fIattr\fP,

    int \fIrobust\fP);

.fi

.SH DESCRIPTION

The

\fIpthread_mutexattr_getrobust\fR()

and

\fIpthread_mutexattr_setrobust\fR()

functions, respectively, shall get and set the mutex

.IR robust

attribute. This attribute is set in the

.IR robust

parameter. Valid values for

.IR robust

include:

.IP PTHREAD_MUTEX_STALLED 6

.br

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.

.br

This is the default value.

.IP PTHREAD_MUTEX_ROBUST 6

.br

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

.BR [EOWNERDEAD] 

from the locking function. If the owning 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

.BR [EOWNERDEAD] .

The notified thread can then attempt to mark the state protected by the

mutex as consistent again by a call to

\fIpthread_mutex_consistent\fR().

After a subsequent successful call to

\fIpthread_mutex_unlock\fR(),

the mutex lock shall be released and can be used normally by other

threads. If the mutex is unlocked without a call to

\fIpthread_mutex_consistent\fR(),

it shall be in a permanently unusable state and all attempts to lock

the mutex shall fail with the error

.BR [ENOTRECOVERABLE] .

The only permissible operation on such a mutex is

\fIpthread_mutex_destroy\fR().

.P

The behavior is undefined if the value specified by the

.IR attr

argument to

\fIpthread_mutexattr_getrobust\fR()

or

\fIpthread_mutexattr_setrobust\fR()

does not refer to an initialized mutex attributes object.

.SH "RETURN VALUE"

Upon successful completion, the

\fIpthread_mutexattr_getrobust\fR()

function shall return zero and store the value of the

.IR robust

attribute of

.IR attr

into the object referenced by the

.IR robust

parameter. Otherwise, an error value shall be returned to indicate the

error. If successful, the

\fIpthread_mutexattr_setrobust\fR()

function shall return zero; otherwise, an error number shall be

returned to indicate the error.

.SH ERRORS

The

\fIpthread_mutexattr_setrobust\fR()

function shall fail if:

.TP

.BR EINVAL

The value of

.IR robust

is invalid.

.P

These functions shall not return an error code of

.BR [EINTR] .

.LP

.IR "The following sections are informative."

.SH EXAMPLES

None.

.SH "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

\fIpthread_mutex_unlock\fR()

without a prior call to

\fIpthread_mutex_consistent\fR().

.P

If the state is declared inconsistent by calling

\fIpthread_mutex_unlock\fR()

without a prior call to

\fIpthread_mutex_consistent\fR(),

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

\fIpthread_mutex_destroy\fR()

results in undefined behavior.

.SH RATIONALE

If an implementation detects that the value specified by the

.IR attr

argument to

\fIpthread_mutexattr_getrobust\fR()

or

\fIpthread_mutexattr_setrobust\fR()

does not refer to an initialized mutex attributes object, it is

recommended that the function should fail and report an

.BR [EINVAL] 

error.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "\fIpthread_mutex_consistent\fR\^(\|)",

.IR "\fIpthread_mutex_destroy\fR\^(\|)",

.IR "\fIpthread_mutex_lock\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<pthread.h>\fP"

.SH 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

Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .