pthread_kill3thr
Handling of signals in threads
Part of pthread_sigmask(3thr).
Usage
#include <pthread.h>
#include <signal.h>
int pthread_sigmask(int how, const sigset_t *newmask, sigset_t *oldmask);
int pthread_kill(pthread_t thread, int signo);
int sigwait(const sigset_t *set, int *sig);
Overview
pthread_sigmask changes the signal mask for the calling thread as described by the how and newmask arguments. If oldmask is not NULL, the previous signal mask is stored in the location pointed to by oldmask.
The meaning of the how and newmask arguments is the same as for sigprocmask(2). If how is SIG_SETMASK, the signal mask is set to newmask. If how is SIG_BLOCK, the signals specified to newmask are added to the current signal mask. If how is SIG_UNBLOCK, the signals specified to newmask are removed from the current signal mask.
Recall that signal masks are set on a per-thread basis, but signal actions and signal handlers, as set with sigaction(2), are shared between all threads.
pthread_kill send signal number signo to the thread thread. The signal is delivered and handled as described in kill(2).
sigwait suspends the calling thread until one of the signals in set is delivered to the calling thread. It then stores the number of the signal received in the location pointed to by sig and returns. The signals in set must be blocked and not ignored on entrance to sigwait. If the delivered signal has a signal handler function attached, that function is not called.
Cancellation
sigwait is a cancellation point.
Return value
On success, 0 is returned. On failure, a non-zero error code is returned.
Errors
The pthread_sigmask function returns the following error codes on error:
EINVAL
|
how is not one of |
|---|---|
EFAULT
|
newmask or oldmask point to invalid addresses |
The pthread_kill function returns the following error codes on error:
EINVAL
|
signo is not a valid signal number |
|---|---|
ESRCH
|
the thread thread does not exist (e.g. it has already terminated) |
The sigwait function never returns an error.
Notes
For sigwait to work reliably, the signals being waited for must be blocked in all threads, not only in the calling thread, since otherwise the POSIX semantics for signal delivery do not guarantee that it's the thread doing the sigwait that will receive the signal. The best way to achieve this is block those signals before any threads are created, and never unblock them in the program other than by calling sigwait.
Releases
4 releases since Debian 1.3 (Bo); the text changed 1 time.