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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.

#include <pthread.h> int pthread_mutexattr_getprotocol(const pthread_mutexattr_t *restrictattr, int *restrictprotocol); int pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr, intprotocol);

DESCRIPTION top

Thepthread_mutexattr_getprotocol() andpthread_mutexattr_setprotocol() functions, respectively, shall get and set the protocol attribute of a mutex attributes object pointed to byattr which was previously created by the functionpthread_mutexattr_init(). Theprotocol attribute defines the protocol to be followed in utilizing mutexes. The value ofprotocol may be one of: PTHREAD_PRIO_INHERIT PTHREAD_PRIO_NONE PTHREAD_PRIO_PROTECT which are defined in the<pthread.h> header. The default value of the attribute shall be PTHREAD_PRIO_NONE. When a thread owns a mutex with the PTHREAD_PRIO_NONEprotocol attribute, its priority and scheduling shall not be affected by its mutex ownership. When a thread is blocking higher priority threads because of owning one or more robust mutexes with the PTHREAD_PRIO_INHERITprotocol attribute, it shall execute at the higher of its priority or the priority of the highest priority thread waiting on any of the robust mutexes owned by this thread and initialized with this protocol. When a thread is blocking higher priority threads because of owning one or more non-robust mutexes with the PTHREAD_PRIO_INHERITprotocol attribute, it shall execute at the higher of its priority or the priority of the highest priority thread waiting on any of the non-robust mutexes owned by this thread and initialized with this protocol. When a thread owns one or more robust mutexes initialized with the PTHREAD_PRIO_PROTECT protocol, it shall execute at the higher of its priority or the highest of the priority ceilings of all the robust mutexes owned by this thread and initialized with this attribute, regardless of whether other threads are blocked on any of these robust mutexes or not. When a thread owns one or more non-robust mutexes initialized with the PTHREAD_PRIO_PROTECT protocol, it shall execute at the higher of its priority or the highest of the priority ceilings of all the non-robust mutexes owned by this thread and initialized with this attribute, regardless of whether other threads are blocked on any of these non-robust mutexes or not. While a thread is holding a mutex which has been initialized with the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT protocol attributes, it shall not be subject to being moved to the tail of the scheduling queue at its priority in the event that its original priority is changed, such as by a call tosched_setparam(). Likewise, when a thread unlocks a mutex that has been initialized with the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT protocol attributes, it shall not be subject to being moved to the tail of the scheduling queue at its priority in the event that its original priority is changed. If a thread simultaneously owns several mutexes initialized with different protocols, it shall execute at the highest of the priorities that it would have obtained by each of these protocols. When a thread makes a call topthread_mutex_lock(), the mutex was initialized with the protocol attribute having the value PTHREAD_PRIO_INHERIT, when the calling thread is blocked because the mutex is owned by another thread, that owner thread shall inherit the priority level of the calling thread as long as it continues to own the mutex. The implementation shall update its execution priority to the maximum of its assigned priority and all its inherited priorities. Furthermore, if this owner thread itself becomes blocked on another mutex with theprotocol attribute having the value PTHREAD_PRIO_INHERIT, the same priority inheritance effect shall be propagated to this other owner thread, in a recursive manner. The behavior is undefined if the value specified by theattr argument topthread_mutexattr_getprotocol() orpthread_mutexattr_setprotocol() does not refer to an initialized mutex attributes object.

Upon successful completion, thepthread_mutexattr_getprotocol() andpthread_mutexattr_setprotocol() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

ERRORS top

Thepthread_mutexattr_setprotocol() function shall fail if:ENOTSUP The value specified byprotocol is an unsupported value. Thepthread_mutexattr_getprotocol() andpthread_mutexattr_setprotocol() functions may fail if:EINVALThe value specified byprotocol is invalid.EPERMThe caller does not have the privilege to perform the operation. These functions shall not return an error code of[EINTR].The following sections are informative.

RATIONALE top

If an implementation detects that the value specified by theattr argument topthread_mutexattr_getprotocol() orpthread_mutexattr_setprotocol() does not refer to an initialized mutex attributes object, it is recommended that the function should fail and report an[EINVAL]error.

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 athttp://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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group 2017PTHREAD...PROTOCOL(3P)

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