mirror of https://github.com/mkerrisk/man-pages
115 lines
3.9 KiB
Plaintext
115 lines
3.9 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "SEM_TIMEDWAIT" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" sem_timedwait
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.SH NAME
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sem_timedwait \- lock a semaphore (\fBADVANCED REALTIME\fP)
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.SH SYNOPSIS
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.LP
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\fB#include <semaphore.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 sem_timedwait(sem_t *restrict\fP \fIsem\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 \fIsem_timedwait\fP() function shall lock the semaphore referenced
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by \fIsem\fP as in the \fIsem_wait\fP() function. However, if the
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semaphore cannot be locked without waiting for another
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process or thread to unlock the semaphore by performing a \fIsem_post\fP()
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function, this
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wait shall be terminated when the specified timeout expires.
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.LP
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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
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timeouts are based (that is, when the value of that clock equals or
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exceeds \fIabs_timeout\fP), or if the absolute time specified
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by \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,
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the timeout shall be based on the system clock as returned by the
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\fItime\fP() function. The
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resolution of the timeout shall be the resolution of the clock on
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which it is based. The \fBtimespec\fP data type is defined as a
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structure in the \fI<time.h>\fP header.
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.LP
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Under no circumstance shall the function fail with a timeout if the
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semaphore can be locked immediately. The validity of the
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\fIabs_timeout\fP need not be checked if the semaphore can be locked
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immediately.
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.SH RETURN VALUE
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.LP
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The \fIsem_timedwait\fP() function shall return zero if the calling
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process successfully performed the semaphore lock operation
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on the semaphore designated by \fIsem\fP. If the call was unsuccessful,
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the state of the semaphore shall be unchanged, and the
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function shall return a value of -1 and set \fIerrno\fP to indicate
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the error.
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.SH ERRORS
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.LP
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The \fIsem_timedwait\fP() function shall fail if:
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.TP 7
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.B EINVAL
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The \fIsem\fP argument does not refer to a valid semaphore.
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.TP 7
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.B EINVAL
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The process or thread would have blocked, and the \fIabs_timeout\fP
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parameter specified a nanoseconds field value less than
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zero or greater than or equal to 1000 million.
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.TP 7
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.B ETIMEDOUT
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The semaphore could not be locked before the specified timeout expired.
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.sp
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.LP
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The \fIsem_timedwait\fP() function may fail if:
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.TP 7
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.B EDEADLK
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A deadlock condition was detected.
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.TP 7
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.B EINTR
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A signal interrupted this function.
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.sp
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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 these functions 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 \fIsem_timedwait\fP() function is part of the Semaphores and Timeouts
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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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\fIsem_post\fP() , \fIsem_trywait\fP() , \fIsem_wait\fP() , \fIsemctl\fP()
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, \fIsemget\fP() , \fIsemop\fP() , \fItime\fP() , the Base Definitions
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volume of
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IEEE\ Std\ 1003.1-2001, \fI<semaphore.h>\fP, \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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