установить / получить тип блокировки чтения-записи объекта атрибута блокировки чтения-записи потока (set/get the read-write lock kind of the thread read-write lock attribute object)
Имя (Name)
pthread_rwlockattr_setkind_np, pthread_rwlockattr_getkind_np -
set/get the read-write lock kind of the thread read-write lock
attribute object
Синопсис (Synopsis)
#include <pthread.h>
int pthread_rwlockattr_setkind_np(pthread_rwlockattr_t *attr,
int pref);
int pthread_rwlockattr_getkind_np(
const pthread_rwlockattr_t *restrict attr,
int *restrict pref);
Compile and link with -pthread.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
pthread_rwlockattr_setkind_np(), pthread_rwlockattr_getkind_np():
_XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200809L
Описание (Description)
The pthread_rwlockattr_setkind_np() function sets the "lock kind"
attribute of the read-write lock attribute object referred to by
attr to the value specified in pref. The argument pref may be
set to one of the following:
PTHREAD_RWLOCK_PREFER_READER_NP
This is the default. A thread may hold multiple read
locks; that is, read locks are recursive. According to
The Single Unix Specification, the behavior is unspecified
when a reader tries to place a lock, and there is no write
lock but writers are waiting. Giving preference to the
reader, as is set by PTHREAD_RWLOCK_PREFER_READER_NP,
implies that the reader will receive the requested lock,
even if a writer is waiting. As long as there are
readers, the writer will be starved.
PTHREAD_RWLOCK_PREFER_WRITER_NP
This is intended as the write lock analog of
PTHREAD_RWLOCK_PREFER_READER_NP. This is ignored by glibc
because the POSIX requirement to support recursive read
locks would cause this option to create trivial deadlocks;
instead use PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP
which ensures the application developer will not take
recursive read locks thus avoiding deadlocks.
PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP
Setting the lock kind to this avoids writer starvation as
long as any read locking is not done in a recursive
fashion.
The pthread_rwlockattr_getkind_np() function returns the value of
the lock kind attribute of the read-write lock attribute object
referred to by attr in the pointer pref.
Возвращаемое значение (Return value)
On success, these functions return 0. Given valid pointer
arguments, pthread_rwlockattr_getkind_np() always succeeds. On
error, pthread_rwlockattr_setkind_np() returns a nonzero error
number.
Ошибки (Error)
EINVAL pref specifies an unsupported value.
Версии (Versions)
The pthread_rwlockattr_getkind_np() and
pthread_rwlockattr_setkind_np() functions first appeared in glibc
2.1.
Стандарты (Conforming to)
These functions are non-standard GNU extensions; hence the suffix
"_np" (nonportable) in the names.
Смотри также (See also)
pthreads(7)
