HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. |  |
NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |STANDARDS |HISTORY |SEE ALSO |COLOPHON | |
pthread_...etkind_np(3) Library Functions Manualpthread_...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,intpref);int pthread_rwlockattr_getkind_np(const pthread_rwlockattr_t *restrictattr,int *restrictpref); Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):pthread_rwlockattr_setkind_np(),pthread_rwlockattr_getkind_np(): _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200809L
Thepthread_rwlockattr_setkind_np() function sets the "lock kind" attribute of the read-write lock attribute object referred to byattr to the value specified inpref. The argumentpref 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 byPTHREAD_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 ofPTHREAD_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 usePTHREAD_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. Thepthread_rwlockattr_getkind_np() function returns the value of the lock kind attribute of the read-write lock attribute object referred to byattr in the pointerpref.
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.
EINVALpref specifies an unsupported value.
GNU; hence the suffix "_np" (nonportable) in the names.
glibc 2.1.
pthreads(7)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17pthread_...etkind_np(3)Pages that refer to this page:pthreads(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |