diff options
author | David Leonard <d@cvs.openbsd.org> | 1998-11-09 03:13:22 +0000 |
---|---|---|
committer | David Leonard <d@cvs.openbsd.org> | 1998-11-09 03:13:22 +0000 |
commit | ff47464de5e68e9c49fe312c953f54b2e90f546c (patch) | |
tree | 4ec0e7f13d619e1b5bf6abfd7125a4ec17569568 /lib/libc_r/man/pthread_rwlock_rdlock.3 | |
parent | 1b2b2c2386c6cc5ebffc769b8a39b80d47e4e0d0 (diff) |
sync with FreeBSD (rwlock, gc thread, man pages)
add (broken) mips md stuff
fix some const warnings
add sigaltstack() stub
another hash at getting shlib auto-init to work (mips/elf and i386/a.out)
Diffstat (limited to 'lib/libc_r/man/pthread_rwlock_rdlock.3')
-rw-r--r-- | lib/libc_r/man/pthread_rwlock_rdlock.3 | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/lib/libc_r/man/pthread_rwlock_rdlock.3 b/lib/libc_r/man/pthread_rwlock_rdlock.3 new file mode 100644 index 00000000000..6bfd3f9ce74 --- /dev/null +++ b/lib/libc_r/man/pthread_rwlock_rdlock.3 @@ -0,0 +1,123 @@ +.\" Copyright (c) 1998 Alex Nash +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $Id: pthread_rwlock_rdlock.3,v 1.1 1998/11/09 03:13:16 d Exp $ +.\" $OpenBSD: pthread_rwlock_rdlock.3,v 1.1 1998/11/09 03:13:16 d Exp $ +.\" +.Dd August 4, 1998 +.Dt PTHREAD_RWLOCK_RDLOCK 3 +.Os +.Sh NAME +.Nm pthread_rwlock_rdlock , +.Nm pthread_rwlock_tryrdlock +.Nd acquire a read/write lock for reading +.Sh SYNOPSIS +.Fd #include <pthread.h> +.Ft int +.Fn pthread_rwlock_rdlock "pthread_rwlock_t *lock" +.Ft int +.Fn pthread_rwlock_tryrdlock "pthread_rwlock_t *lock" +.Sh DESCRIPTION +The +.Fn pthread_rwlock_rdlock +function acquires a read lock on +.Fa lock +provided that +.Fa lock +is not presently held for writing and no writer threads are +presently blocked on the lock. If the read lock cannot be +immediately acquired, the calling thread blocks until it can +acquire the lock. +.Pp +The +.Fn pthread_rwlock_tryrdlock +function performs the same action, but does not block if the lock +cannot be immediately obtained (i.e. the lock is held for writing +or there are waiting writers). +.Pp +A thread may hold multiple concurrent read locks. If so, +.Fn pthread_rwlock_unlock +must be called once for each lock obtained. +.Pp +The results of acquiring a read lock while the calling thread holds +a write lock are undefined. +.Sh IMPLEMENTATION NOTES +To prevent writer starvation, writers are favored over readers. +.Sh RETURN VALUES +If successful, the +.Fn pthread_rwlock_rdlock +and +.Fn pthread_rwlock_tryrdlock +functions will return zero. Otherwise an error number will be returned +to indicate the error. +.Sh SEE ALSO +.Xr pthread_rwlock_init 3 , +.Xr pthread_rwlock_trywrlock 3 , +.Xr pthread_rwlock_unlock 3 , +.Xr pthread_rwlock_wrlock 3 +.Sh STANDARDS +The +.Fn pthread_rwlock_rdlock +and +.Fn pthread_rwlock_tryrdlock +functions are expected to conform to +.St -susv2 . +.Sh ERRORS +The +.Fn pthread_rwlock_tryrdlock +function will fail if: +.Bl -tag -width Er +.It Bq Er EBUSY +The lock could not be acquired because a writer holds the lock or +was blocked on it. +.El +.Pp +The +.Fn pthread_rwlock_rdlock +and +.Fn pthread_rwlock_tryrdlock +functions may fail if: +.Bl -tag -width Er +.It Bq Er EAGAIN +The lock could not be acquired because the maximum number of read locks +against +.Fa lock +has been exceeded. +.It Bq Er EDEADLK +The current thread already owns +.Fa lock +for writing. +.It Bq Er EINVAL +The value specified by +.Fa lock +is invalid. +.It Bq Er ENOMEM +Insufficient memory exists to initialize the lock (applies to +statically initialized locks only). +.El +.Sh HISTORY +The +.Fn pthread_rwlock_rdlock +function first appeared in +.Fx 3.0 . |