получить и установить надежный атрибут мьютекса (get and set the mutex robust attribute)
Пролог (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.
Имя (Name)
pthread_mutexattr_getrobust, pthread_mutexattr_setrobust — get
and set the mutex robust attribute
Синопсис (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);
Описание (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.
Возвращаемое значение (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.
Ошибки (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.
Примеры (Examples)
None.
Использование в приложениях (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.
Обоснование (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.
Будущие направления (Future directions)
None.
Смотри также (See also)
pthread_mutex_consistent(3p), pthread_mutex_destroy(3p),
pthread_mutex_lock(3p)
The Base Definitions volume of POSIX.1‐2017, pthread.h(0p)
