mirror of https://github.com/mkerrisk/man-pages
124 lines
4.5 KiB
Plaintext
124 lines
4.5 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "PTHREAD_RWLOCK_TIMEDRDLOCK" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" pthread_rwlock_timedrdlock
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.SH NAME
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pthread_rwlock_timedrdlock \- lock a read-write lock for reading
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.SH SYNOPSIS
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.LP
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\fB#include <pthread.h>
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.br
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#include <time.h>
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.br
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.sp
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int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict\fP \fIrwlock\fP\fB,
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.br
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\ \ \ \ \ \ const struct timespec *restrict\fP \fIabs_timeout\fP\fB);
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\fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIpthread_rwlock_timedrdlock\fP() function shall apply a read
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lock to the read-write lock referenced by \fIrwlock\fP as
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in the \fIpthread_rwlock_rdlock\fP() function. However, if the lock
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cannot
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be acquired without waiting for other threads to unlock the lock,
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this wait shall be terminated when the specified timeout expires.
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The timeout shall expire when the absolute time specified by \fIabs_timeout\fP
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passes, as measured by the clock on which timeouts
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are based (that is, when the value of that clock equals or exceeds
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\fIabs_timeout\fP), or if the absolute time specified by
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\fIabs_timeout\fP has already been passed at the time of the call.
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.LP
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If the Timers option is supported, the timeout shall be based on the
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CLOCK_REALTIME clock. If the Timers option is not supported, the
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timeout shall be based on the system clock as returned by the
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\fItime\fP() function. The resolution of the timeout shall be the
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resolution of the clock on
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which it is based. The \fBtimespec\fP data type is defined in the
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\fI<time.h>\fP
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header. Under no circumstances shall the function fail with a timeout
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if the lock can be acquired immediately. The validity of the
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\fIabs_timeout\fP parameter need not be checked if the lock can be
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immediately acquired.
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.LP
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If a signal that causes a signal handler to be executed is delivered
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to a thread blocked on a read-write lock via a call to
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\fIpthread_rwlock_timedrdlock\fP(), upon return from the signal handler
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the thread shall resume waiting for the lock as if it was
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not interrupted.
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.LP
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The calling thread may deadlock if at the time the call is made it
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holds a write lock on \fIrwlock\fP. The results are
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undefined if this function is called with an uninitialized read-write
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lock.
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.SH RETURN VALUE
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.LP
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The \fIpthread_rwlock_timedrdlock\fP() function shall return zero
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if the lock for reading on the read-write lock object
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referenced by \fIrwlock\fP is acquired. Otherwise, an error number
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shall be returned to indicate the error.
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.SH ERRORS
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.LP
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The \fIpthread_rwlock_timedrdlock\fP() function shall fail if:
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.TP 7
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.B ETIMEDOUT
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The lock could not be acquired before the specified timeout expired.
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.sp
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.LP
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The \fIpthread_rwlock_timedrdlock\fP() function may fail if:
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.TP 7
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.B EAGAIN
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The read lock could not be acquired because the maximum number of
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read locks for lock would be exceeded.
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.TP 7
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.B EDEADLK
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The calling thread already holds a write lock on \fIrwlock\fP.
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.TP 7
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.B EINVAL
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The value specified by \fIrwlock\fP does not refer to an initialized
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read-write lock object, or the \fIabs_timeout\fP
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nanosecond value is less than zero or greater than or equal to 1000
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million.
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.sp
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.LP
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This function shall not return an error code of [EINTR].
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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Applications using this function may be subject to priority inversion,
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as discussed in the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, Section 3.285, Priority Inversion.
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.LP
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The \fIpthread_rwlock_timedrdlock\fP() function is part of the Threads
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and Timeouts options and need not be provided on all
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implementations.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIpthread_rwlock_destroy\fP() , \fIpthread_rwlock_rdlock\fP() , \fIpthread_rwlock_timedwrlock\fP()
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, \fIpthread_rwlock_tryrdlock\fP() , \fIpthread_rwlock_trywrlock\fP()
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, \fIpthread_rwlock_unlock\fP() , \fIpthread_rwlock_wrlock\fP() ,
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the Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<pthread.h>\fP,
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\fI<time.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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