sigsuspend(2) System Calls Manual sigsuspend(2)
NAME
sigsuspend, rt_sigsuspend - wait for a signal
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <signal.h>
int sigsuspend(const sigset_t *mask);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sigsuspend():
_POSIX_C_SOURCE
DESCRIPTION
sigsuspend() temporarily replaces the signal mask of the calling thread
with the mask given by mask and then suspends the thread until delivery
of a signal whose action is to invoke a signal handler or to terminate a
process.
If the signal terminates the process, then sigsuspend() does not return.
If the signal is caught, then sigsuspend() returns after the signal han-
dler returns, and the signal mask is restored to the state before the
call to sigsuspend().
It is not possible to block SIGKILL or SIGSTOP; specifying these signals
in mask, has no effect on the thread's signal mask.
RETURN VALUE
sigsuspend() always returns -1, with errno set to indicate the error
(normally, EINTR).
ERRORS
EFAULT mask points to memory which is not a valid part of the process
address space.
EINTR The call was interrupted by a signal; signal(7).
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001.
C library/kernel differences
The original Linux system call was named sigsuspend(). However, with
the addition of real-time signals in Linux 2.2, the fixed-size, 32-bit
sigset_t type supported by that system call was no longer fit for pur-
pose. Consequently, a new system call, rt_sigsuspend(), was added to
support an enlarged sigset_t type. The new system call takes a second
argument, size_t sigsetsize, which specifies the size in bytes of the
signal set in mask. This argument is currently required to have the
value sizeof(sigset_t) (or the error EINVAL results). The glibc sigsus-
pend() wrapper function hides these details from us, transparently call-
ing rt_sigsuspend() when the kernel provides it.
NOTES
Normally, sigsuspend() is used in conjunction with sigprocmask(2) in or-
der to prevent delivery of a signal during the execution of a critical
code section. The caller first blocks the signals with sigprocmask(2).
When the critical code has completed, the caller then waits for the sig-
nals by calling sigsuspend() with the signal mask that was returned by
sigprocmask(2) (in the oldset argument).
See sigsetops(3) for details on manipulating signal sets.
SEE ALSO
kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2), sigwait-
info(2), sigsetops(3), sigwait(3), signal(7)
Linux man-pages 6.9.1 2024-05-02 sigsuspend(2)
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