NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | ATTRIBUTES | SEE ALSO | NOTES
#include <signal.h>int sigsuspend(const sigset_t *set);
The sigsuspend() function replaces the caller's signal mask with the set of signals pointed to by the set argument and suspends the caller until delivery of a signal whose action is either to execute a signal catching function or to terminate the process.
If the action is to terminate the process, sigsuspend() does not return. If the action is to execute a signal catching function, sigsuspend() returns after the signal catching function returns. On return, the signal mask is restored to the set that existed before the call to sigsuspend(). See NOTES for the precise semantics of signal mask restoration in a multithreaded process.
It is not possible to block those signals that cannot be ignored (see signal(3HEAD)); this restriction is silently imposed by the system.
Since sigsuspend() suspends process execution indefinitely, there is no successful completion return value. On failure, it returns -1 and sets errno to indicate the error.
The sigsuspend() function will fail if:
The set argument points to an illegal address.
A signal was caught by the calling process and control was returned from the signal catching function.
See attributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE | ATTRIBUTE VALUE |
---|---|
MT-Level | Async-Signal-Safe |
In a multithreaded application, the sigwait(2), function should be used instead of sigsuspend(). Should sigsuspend() be used, however, its semantics of signal mask restoration are slightly different from those for a single-threaded process on return from the signal catching function, the signal mask is restored to the set that existed before the call to sigsuspend(). This action raises the following implications:
If a thread specifies two signals in the mask to sigsuspend(), both signals could interrupt its call to sigsuspend() simultaneously. In the traditional program that does not use threads, a call to sigsuspend() with two signals in the mask always returns with only one signal delivered. The other signal remains pending if masked earlier, unlike the MT case.
While a thread is executing the signal handler that interrupted its call to sigsuspend(), its signal mask is the one passed to sigsuspend(). It does not get restored to the previous mask until it returns from all the signal handlers that interrupted sigsuspend().
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | ATTRIBUTES | SEE ALSO | NOTES