e4c096aeb4
Passing an invalid pointer results in undefined behaviour. The wrappers in libthr access some of the data pointed to by the arguments in userland, so that an invalid pointer will cause a signal and not an [EFAULT] error return. Furthermore, if the [EFAULT] error occurs when the kernel is writing, it is not a proper error in the sense that the call still commits (changing the signal disposition or accepting the signal). MFC after: 1 week
207 lines
5.2 KiB
Groff
207 lines
5.2 KiB
Groff
.\" Copyright (c) 2005 David Xu <davidxu@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
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.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 27, 2012
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.Dt SIGTIMEDWAIT 2
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.Os
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.Sh NAME
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.Nm sigtimedwait , sigwaitinfo
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.Nd "wait for queued signals (REALTIME)"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In signal.h
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.Ft int
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.Fo sigtimedwait
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.Fa "const sigset_t *restrict set" "siginfo_t *restrict info"
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.Fa "const struct timespec *restrict timeout"
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.Fc
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.Ft int
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.Fn sigwaitinfo "const sigset_t * restrict set" "siginfo_t * restrict info"
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.Sh DESCRIPTION
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The
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.Fn sigtimedwait
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system call is equivalent to
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.Fn sigwaitinfo
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except that if none of the signals specified by
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.Fa set
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are pending,
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.Fn sigtimedwait
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waits for the time interval specified in the
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.Vt timespec
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structure referenced by
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.Fa timeout .
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If the
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.Vt timespec
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structure pointed to by
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.Fa timeout
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is zero-valued and if none of the signals specified by
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.Fa set
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are pending, then
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.Fn sigtimedwait
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returns immediately with an error.
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If
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.Fa timeout
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is the
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.Dv NULL
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pointer, the behavior is unspecified.
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.Dv CLOCK_MONOTONIC
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clock is used to measure the time interval specified by the
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.Fa timeout
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argument.
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.Pp
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The
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.Fn sigwaitinfo
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system call selects the pending signal from the set specified by
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.Fa set .
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Should any of multiple pending signals in the range
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.Dv SIGRTMIN
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to
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.Dv SIGRTMAX
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be selected, it shall be the lowest numbered one.
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The
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selection order between realtime and non-realtime signals, or
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between multiple pending non-realtime signals, is unspecified.
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If no signal in
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.Fa set
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is pending at the time of the call, the calling thread
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is suspended until one or more signals in
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.Fa set
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become pending or until it is interrupted by an unblocked, caught signal.
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.Pp
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The
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.Fn sigwaitinfo
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system call is equivalent to the
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.Fn sigwait
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system call if the
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.Fa info
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argument is
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.Dv NULL .
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If the
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.Fa info
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argument is
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.Pf non- Dv NULL ,
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the
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.Fn sigwaitinfo
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function is equivalent to
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.Fn sigwait ,
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except that the selected signal number shall be stored in the
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.Va si_signo
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member, and the cause of the signal shall be stored in the
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.Va si_code
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member.
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Besides this, the
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.Fn sigwaitinfo
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and
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.Fn sigtimedwait
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system calls may return
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.Er EINTR
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if interrupted by signal, which is not allowed for the
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.Fn sigwait
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function.
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.Pp
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If any value is queued to the selected signal, the first such queued
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value is dequeued and, if the info argument is
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.Pf non- Dv NULL ,
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the value is stored in the
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.Va si_value
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member of
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.Fa info .
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The system resource used to queue the signal
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is released and returned to the system for other use.
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If no value is queued,
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the content of the
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.Va si_value
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member is zero-valued.
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If no further signals are
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queued for the selected signal, the pending indication for that signal
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is reset.
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.Sh RETURN VALUES
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Upon successful completion (that is, one of the signals specified by
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.Fa set
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is pending or is generated)
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.Fn sigwaitinfo
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and
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.Fn sigtimedwait
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return the selected signal number.
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Otherwise, the functions return a value of \-1
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and set the global variable
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.Va errno
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to indicate the error.
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.Sh ERRORS
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The
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.Fn sigtimedwait
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EAGAIN
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No signal specified by set was generated within the specified timeout period.
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.El
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.Pp
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The
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.Fn sigtimedwait
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and
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.Fn sigwaitinfo
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system calls fail if:
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.Bl -tag -width Er
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.It Bq Er EINTR
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The wait was interrupted by an unblocked, caught signal.
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.Pp
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.El
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The
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.Fn sigtimedwait
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system call may also fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa timeout
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argument specified a
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.Va tv_nsec
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value less than zero or greater than or equal
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to 1000 million.
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Kernel only checks for this error if no signal is pending in set and it
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is necessary to wait.
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.El
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.Sh SEE ALSO
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.Xr sigaction 2 ,
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.Xr sigpending 2 ,
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.Xr sigqueue 2 ,
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.Xr sigsuspend 2 ,
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.Xr sigwait 2 ,
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.Xr pause 3 ,
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.Xr pthread_sigmask 3 ,
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.Xr siginfo 3
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.Sh STANDARDS
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The
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.Fn sigtimedwait
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and
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.Fn sigwaitinfo
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system calls conform to
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.St -p1003.1-96 .
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