SIGSUSPEND(2) Linux Programmer's Manual SIGSUSPEND(2)
sigsuspend, rt_sigsuspend - wait for a signal
int sigsuspend(const sigset_t *mask);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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
If the signal terminates the process, then sigsuspend() does not re-
turn. If the signal is caught, then sigsuspend() returns after the
signal handler 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 sig-
nals in mask, has no effect on the thread's signal mask.
sigsuspend() always returns -1, with errno set to indicate the error
EFAULT mask points to memory which is not a valid part of the process
EINTR The call was interrupted by a signal; signal(7).
Normally, sigsuspend() is used in conjunction with sigprocmask(2) in
order to prevent delivery of a signal during the execution of a criti-
cal code section. The caller first blocks the signals with sigproc-
mask(2). When the critical code has completed, the caller then waits
for the signals 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.
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 sig-
suspend() wrapper function hides these details from us, transparently
calling rt_sigsuspend() when the kernel provides it.
kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2), sigwait-
info(2), sigsetops(3), sigwait(3), signal(7)
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Linux 2019-03-06 SIGSUSPEND(2)
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