заблокировать мьютекс (lock a mutex)
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_mutex_timedlock — lock a mutex
Синопсис (Synopsis)
#include <pthread.h>
#include <time.h>
int pthread_mutex_timedlock(pthread_mutex_t *restrict mutex,
const struct timespec *restrict abstime);
Описание (Description)
The pthread_mutex_timedlock() function shall lock the mutex
object referenced by mutex. If the mutex is already locked, the
calling thread shall block until the mutex becomes available as
in the pthread_mutex_lock() function. If the mutex cannot be
locked without waiting for another thread to unlock the mutex,
this wait shall be terminated when the specified timeout expires.
The timeout shall expire when the absolute time specified by
abstime passes, as measured by the clock on which timeouts are
based (that is, when the value of that clock equals or exceeds
abstime), or if the absolute time specified by abstime has
already been passed at the time of the call.
The timeout shall be based on the CLOCK_REALTIME clock. The
resolution of the timeout shall be the resolution of the clock on
which it is based. The timespec data type is defined in the
<time.h> header.
Under no circumstance shall the function fail with a timeout if
the mutex can be locked immediately. The validity of the abstime
parameter need not be checked if the mutex can be locked
immediately.
As a consequence of the priority inheritance rules (for mutexes
initialized with the PRIO_INHERIT protocol), if a timed mutex
wait is terminated because its timeout expires, the priority of
the owner of the mutex shall be adjusted as necessary to reflect
the fact that this thread is no longer among the threads waiting
for the mutex.
If mutex is a robust mutex and the process containing the owning
thread terminated while holding the mutex lock, a call to
pthread_mutex_timedlock() shall return the error value
[EOWNERDEAD]. If mutex is a robust mutex and the owning thread
terminated while holding the mutex lock, a call to
pthread_mutex_timedlock() may return the error value [EOWNERDEAD]
even if the process in which the owning thread resides has not
terminated. In these cases, the mutex is locked by the thread but
the state it protects is marked as inconsistent. The application
should ensure that the state is made consistent for reuse and
when that is complete call pthread_mutex_consistent(). If the
application is unable to recover the state, it should unlock the
mutex without a prior call to pthread_mutex_consistent(), after
which the mutex is marked permanently unusable.
If mutex does not refer to an initialized mutex object, the
behavior is undefined.
Возвращаемое значение (Return value)
If successful, the pthread_mutex_timedlock() function shall
return zero; otherwise, an error number shall be returned to
indicate the error.
Ошибки (Error)
The pthread_mutex_timedlock() function shall fail if:
EAGAIN The mutex could not be acquired because the maximum number
of recursive locks for mutex has been exceeded.
EDEADLK
The mutex type is PTHREAD_MUTEX_ERRORCHECK and the current
thread already owns the mutex.
EINVAL The mutex was created with the protocol attribute having
the value PTHREAD_PRIO_PROTECT and the calling thread's
priority is higher than the mutex' current priority
ceiling.
EINVAL The process or thread would have blocked, and the abstime
parameter specified a nanoseconds field value less than
zero or greater than or equal to 1000 million.
ENOTRECOVERABLE
The state protected by the mutex is not recoverable.
EOWNERDEAD
The mutex is a robust mutex and the process containing the
previous owning thread terminated while holding the mutex
lock. The mutex lock shall be acquired by the calling
thread and it is up to the new owner to make the state
consistent.
ETIMEDOUT
The mutex could not be locked before the specified timeout
expired.
The pthread_mutex_timedlock() function may fail if:
EDEADLK
A deadlock condition was detected.
EOWNERDEAD
The mutex is a robust mutex and the previous owning thread
terminated while holding the mutex lock. The mutex lock
shall be acquired by the calling thread and it is up to
the new owner to make the state consistent.
This function shall not return an error code of [EINTR].
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
Applications that have assumed that non-zero return values are
errors will need updating for use with robust mutexes, since a
valid return for a thread acquiring a mutex which is protecting a
currently inconsistent state is [EOWNERDEAD]. Applications that
do not check the error returns, due to ruling out the possibility
of such errors arising, should not use robust mutexes. If an
application is supposed to work with normal and robust mutexes,
it should check all return values for error conditions and if
necessary take appropriate action.
Обоснование (Rationale)
Refer to pthread_mutex_lock(3p).
Будущие направления (Future directions)
None.
Смотри также (See also)
pthread_mutex_destroy(3p), pthread_mutex_lock(3p), time(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.12, Memory
Synchronization, pthread.h(0p), time.h(0p)
