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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | SEE ALSO |
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pthread_...etkind_np(3) Library Functions Manual pthread_...etkind_np(3)
pthread_rwlockattr_setkind_np, pthread_rwlockattr_getkind_np -
set/get the read-write lock kind of the thread read-write lock
attribute object
POSIX threads library (libpthread, -lpthread)
#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);
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
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.
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.
EINVAL pref specifies an unsupported value.
GNU; hence the suffix "_np" (nonportable) in the names.
glibc 2.1.
pthreads(7)
Linux man-pages (unreleased) (date) pthread_...etkind_np(3)
Pages that refer to this page: pthreads(7)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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