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Add an implementation of pthread_rwlock_timed{rd,wr}lock() to libthr with

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attendant documentation.
This commit is contained in:
mtm 2004-01-16 10:52:10 +00:00
parent 5af038f21a
commit e3c786562f
4 changed files with 281 additions and 11 deletions
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65
lib/libthr/thread/thr_rwlock.c
View File

@ -40,13 +40,17 @@
__weak_reference(_pthread_rwlock_destroy, pthread_rwlock_destroy);
__weak_reference(_pthread_rwlock_init, pthread_rwlock_init);
__weak_reference(_pthread_rwlock_rdlock, pthread_rwlock_rdlock);
__weak_reference(_pthread_rwlock_timedrdlock, pthread_rwlock_timedrdlock);
__weak_reference(_pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock);
__weak_reference(_pthread_rwlock_tryrdlock, pthread_rwlock_tryrdlock);
__weak_reference(_pthread_rwlock_trywrlock, pthread_rwlock_trywrlock);
__weak_reference(_pthread_rwlock_unlock, pthread_rwlock_unlock);
__weak_reference(_pthread_rwlock_wrlock, pthread_rwlock_wrlock);
static int rwlock_rdlock_common(pthread_rwlock_t *, int);
static int rwlock_wrlock_common(pthread_rwlock_t *, int);
static int rwlock_rdlock_common(pthread_rwlock_t *, int,
const struct timespec *);
static int rwlock_wrlock_common(pthread_rwlock_t *, int,
const struct timespec *);
int
_pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
@ -116,7 +120,8 @@ out_mutex:
* it is greater than 0 it will return immediately with EBUSY.
*/
static int
rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking)
rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking,
const struct timespec *timeout)
{
pthread_rwlock_t prwlock;
int ret;
@ -124,6 +129,13 @@ rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking)
if (rwlock == NULL || *rwlock == NULL)
return(EINVAL);
/*
* Check for validity of the timeout parameter.
*/
if (timeout != NULL &&
(timeout->tv_nsec < 0 || timeout->tv_nsec >= 1000000000))
return (EINVAL);
prwlock = *rwlock;
/* grab the monitor lock */
@ -143,7 +155,12 @@ rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking)
return (EBUSY);
}
ret = pthread_cond_wait(&prwlock->read_signal, &prwlock->lock);
if (timeout == NULL)
ret = pthread_cond_wait(&prwlock->read_signal,
&prwlock->lock);
else
ret = pthread_cond_timedwait(&prwlock->read_signal,
&prwlock->lock, timeout);
if (ret != 0 && ret != EINTR) {
/* can't do a whole lot if this fails */
@ -168,13 +185,20 @@ rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking)
int
_pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
{
return (rwlock_rdlock_common(rwlock, 0));
return (rwlock_rdlock_common(rwlock, 0, NULL));
}
int
_pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock,
const struct timespec *timeout)
{
return (rwlock_rdlock_common(rwlock, 0, timeout));
}
int
_pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
{
return (rwlock_rdlock_common(rwlock, 1));
return (rwlock_rdlock_common(rwlock, 1, NULL));
}
int
@ -215,13 +239,20 @@ _pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
int
_pthread_rwlock_wrlock (pthread_rwlock_t *rwlock)
{
return (rwlock_wrlock_common(rwlock, 0));
return (rwlock_wrlock_common(rwlock, 0, NULL));
}
int
_pthread_rwlock_timedwrlock (pthread_rwlock_t *rwlock,
const struct timespec *timeout)
{
return (rwlock_wrlock_common(rwlock, 0, timeout));
}
int
_pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock)
{
return (rwlock_wrlock_common(rwlock, 1));
return (rwlock_wrlock_common(rwlock, 1, NULL));
}
/*
@ -229,7 +260,8 @@ _pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock)
* it is greater than 0 it will return immediately with EBUSY.
*/
static int
rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking)
rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking,
const struct timespec *timeout)
{
pthread_rwlock_t prwlock;
int ret;
@ -237,6 +269,13 @@ rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking)
if (rwlock == NULL || *rwlock == NULL)
return(EINVAL);
/*
* Check the timeout value for validity.
*/
if (timeout != NULL &&
(timeout->tv_nsec < 0 || timeout->tv_nsec >= 1000000000))
return (EINVAL);
prwlock = *rwlock;
/* grab the monitor lock */
@ -251,8 +290,12 @@ rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking)
++prwlock->blocked_writers;
ret = pthread_cond_wait(&prwlock->write_signal,
&prwlock->lock);
if (timeout == NULL)
ret = pthread_cond_wait(&prwlock->write_signal,
&prwlock->lock);
else
ret = pthread_cond_timedwait(&prwlock->write_signal,
&prwlock->lock, timeout);
if (ret != 0 && ret != EINTR) {
--prwlock->blocked_writers;

2
share/man/man3/Makefile
View File

@ -155,6 +155,8 @@ MAN+= pthread.3 \
pthread_rwlock_destroy.3 \
pthread_rwlock_init.3 \
pthread_rwlock_rdlock.3 \
pthread_rwlock_timedrdlock.3 \
pthread_rwlock_timedwrlock.3 \
pthread_rwlock_unlock.3 \
pthread_rwlock_wrlock.3 \
pthread_rwlockattr_destroy.3 \

118
share/man/man3/pthread_rwlock_timedrdlock.3 Normal file
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@ -0,0 +1,118 @@
.\" Copyright (c) 2004 Michael Telahun Makonnen
.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd January 16, 2004
.Dt PTHREAD_RWLOCK_TIMEDRDLOCK 3
.Os
.Sh NAME
.Nm pthread_rwlock_timedrdlock ,
.Nd acquire a read-write lock for reading or give up after a specified period
.Sh LIBRARY
.Lb libpthread
.Lb libthr
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_rwlock_timedrdlock "pthread_rwlock_t *rwlock" "const struct timespec *abs_timeout"
.Sh DESCRIPTION
This function acquires a read lock on the read-write lock
.Fa rwlock .
However, if the lock cannot be
acquired without waiting for another thread to
unlock the lock,
this wait shall be terminated when
.Fa abs_timeout
expires.
.Pp
.Pp
A thread may hold multiple concurrent read locks.
The
.Fn pthread_rwlock_unlock
function must be called once for each lock acquired.
.Pp
If the thread should be interrupted by a signal,
the
.Fn pthread_rwlock_wrlock
function will be automatically restarted after the thread returns from
the signal handler.
.Pp
The calling thread may deadlock if
at the time the call is made it holds a write lock on
.Fa rwlock .
The results are undefined if this function is called with
an uninitialized read-write lock.
.Sh IMPLEMENTATION NOTES
To prevent writer starvation, writers are favored over readers.
.Sh RETURN VALUES
If successful, the
.Fn pthread_rwlock_timedrdlock
function will return zero. Otherwise an error number will be returned
to indicate the error.
.Pp
This function shall not return an error code of EINTR.
.Sh ERRORS
The
.Fn pthread_rwlock_timedrdlock
function will fail if:
.Bl -tag -width Er
.It Bq Er ETIMEDOUT
The lock could not be acquired before the specified timeout expired
.El
.Pp
The
.Fn pthread_rwlock_timedrdlock
function may fail if:
.Bl -tag -width Er
.It Bq Er EAGAIN
The read lock could not be
acquired because the maximum number of read locks for
.Fa rwlock
would be exceeded.
.It Bq Er EDEADLK
The calling thread already holds a write lock on
.Fa rwlock .
.It Bq Er EINVAL
The value specified by
.Fa rwlock
does not refer to an initialized read-write lock object,
or the
.Fa abs_timeout nanosecond value is less than zero or
greater than or equal to 1 billion.
.El
.Sh SEE ALSO
.Xr pthread_rwlock_init 3 ,
.Xr pthread_rwlock_timedwrlock 3
.Xr pthread_rwlock_unlock 3 ,
.Sh STANDARDS
The
.Fn pthread_rwlock_timedrdlock
function is expected to conform to
.St -p1003.1-96 .
.Sh HISTORY
The
.Fn pthread_rwlock_timedrdlock
function first appeared in
.Fx 5.2 .

107
share/man/man3/pthread_rwlock_timedwrlock.3 Normal file
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@ -0,0 +1,107 @@
.\" Copyright (c) 2004 Michael Telahun Makonnen
.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd January 16, 2004
.Dt PTHREAD_RWLOCK_TIMEDWRLOCK 3
.Os
.Sh NAME
.Nm pthread_rwlock_timedwrlock ,
.Nd acquire a read-write lock for writing or give up after a specified period
.Sh LIBRARY
.Lb libpthread
.Lb libthr
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_rwlock_timedwrlock "pthread_rwlock_t *rwlock" "const struct timespec *abs_timeout"
.Sh DESCRIPTION
This function acquires a write lock on the read-write lock
.Fa rwlock .
However, if the lock cannot be
acquired without waiting for another thread to
unlock the lock,
this wait shall be terminated when
.Fa abs_timeout
expires.
.Pp
If the thread should be interrupted by a signal,
the
.Fn pthread_rwlock_wrlock
function will be automatically restarted after the thread returns from
the signal handler.
.Pp
The calling thread may deadlock if
at the time the call is made it holds
.Fa rwlock .
The results are undefined if this function is called with
an uninitialized read-write lock.
.Sh IMPLEMENTATION NOTES
To prevent writer starvation, writers are favored over readers.
.Sh RETURN VALUES
If successful, the
.Fn pthread_rwlock_timedwrlock
function will return zero. Otherwise an error number will be returned
to indicate the error.
.Pp
This function shall not return an error code of EINTR.
.Sh ERRORS
The
.Fn pthread_rwlock_timedwrlock
function shall fail if:
.Bl -tag -width Er
.It Bq Er ETIMEDOUT
The lock could not be acquired before the specified timeout expired
.El
.Pp
The
.Fn pthread_rwlock_timedrwlock
function may fail if:
.Bl -tag -width Er
.It Bq Er EDEADLK
The calling thread already holds
.Fa rwlock .
.It Bq Er EINVAL
The value specified by
.Fa rwlock
does not refer to an initialized read-write lock object,
or the
.Fa abs_timeout nanosecond value is less than zero or
greater than or equal to 1 billion.
.El
.Sh SEE ALSO
.Xr pthread_rwlock_init 3 ,
.Xr pthread_rwlock_timedrdlock 3
.Xr pthread_rwlock_unlock 3 ,
.Sh STANDARDS
The
.Fn pthread_rwlock_timedwrlock
function is expected to conform to
.St -p1003.1-96 .
.Sh HISTORY
The
.Fn pthread_rwlock_timedwrlock
function first appeared in
.Fx 5.2 .