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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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PTHREAD_SIGMASK(3P) POSIX Programmer's Manual PTHREAD_SIGMASK(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
pthread_sigmask, sigprocmask — examine and change blocked signals
#include <signal.h>
int pthread_sigmask(int how, const sigset_t *restrict set,
sigset_t *restrict oset);
int sigprocmask(int how, const sigset_t *restrict set,
sigset_t *restrict oset);
The pthread_sigmask() function shall examine or change (or both)
the calling thread's signal mask, regardless of the number of
threads in the process. The function shall be equivalent to
sigprocmask(), without the restriction that the call be made in a
single-threaded process.
In a single-threaded process, the sigprocmask() function shall
examine or change (or both) the signal mask of the calling
thread.
If the argument set is not a null pointer, it points to a set of
signals to be used to change the currently blocked set.
The argument how indicates the way in which the set is changed,
and the application shall ensure it consists of one of the
following values:
SIG_BLOCK The resulting set shall be the union of the current
set and the signal set pointed to by set.
SIG_SETMASK The resulting set shall be the signal set pointed to
by set.
SIG_UNBLOCK The resulting set shall be the intersection of the
current set and the complement of the signal set
pointed to by set.
If the argument oset is not a null pointer, the previous mask
shall be stored in the location pointed to by oset. If set is a
null pointer, the value of the argument how is not significant
and the thread's signal mask shall be unchanged; thus the call
can be used to enquire about currently blocked signals.
If there are any pending unblocked signals after the call to
sigprocmask(), at least one of those signals shall be delivered
before the call to sigprocmask() returns.
It is not possible to block those signals which cannot be
ignored. This shall be enforced by the system without causing an
error to be indicated.
If any of the SIGFPE, SIGILL, SIGSEGV, or SIGBUS signals are
generated while they are blocked, the result is undefined, unless
the signal was generated by the action of another process, or by
one of the functions kill(), pthread_kill(), raise(), or
sigqueue().
If sigprocmask() fails, the thread's signal mask shall not be
changed.
The use of the sigprocmask() function is unspecified in a multi-
threaded process.
Upon successful completion pthread_sigmask() shall return 0;
otherwise, it shall return the corresponding error number.
Upon successful completion, sigprocmask() shall return 0;
otherwise, -1 shall be returned, errno shall be set to indicate
the error, and the signal mask of the process shall be unchanged.
The pthread_sigmask() and sigprocmask() functions shall fail if:
EINVAL The value of the how argument is not equal to one of the
defined values.
The pthread_sigmask() function shall not return an error code of
[EINTR].
The following sections are informative.
Signaling in a Multi-Threaded Process
This example shows the use of pthread_sigmask() in order to deal
with signals in a multi-threaded process. It provides a fairly
general framework that could be easily adapted/extended.
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
...
static sigset_t signal_mask; /* signals to block */
int main (int argc, char *argv[])
{
pthread_t sig_thr_id; /* signal handler thread ID */
int rc; /* return code */
sigemptyset (&signal_mask);
sigaddset (&signal_mask, SIGINT);
sigaddset (&signal_mask, SIGTERM);
rc = pthread_sigmask (SIG_BLOCK, &signal_mask, NULL);
if (rc != 0) {
/* handle error */
...
}
/* any newly created threads inherit the signal mask */
rc = pthread_create (&sig_thr_id, NULL, signal_thread, NULL);
if (rc != 0) {
/* handle error */
...
}
/* APPLICATION CODE */
...
}
void *signal_thread (void *arg)
{
int sig_caught; /* signal caught */
int rc; /* returned code */
rc = sigwait (&signal_mask, &sig_caught);
if (rc != 0) {
/* handle error */
}
switch (sig_caught)
{
case SIGINT: /* process SIGINT */
...
break;
case SIGTERM: /* process SIGTERM */
...
break;
default: /* should normally not happen */
fprintf (stderr, "\nUnexpected signal %d\n", sig_caught);
break;
}
}
None.
When a thread's signal mask is changed in a signal-catching
function that is installed by sigaction(), the restoration of the
signal mask on return from the signal-catching function overrides
that change (see sigaction()). If the signal-catching function
was installed with signal(), it is unspecified whether this
occurs.
See kill() for a discussion of the requirement on delivery of
signals.
None.
exec(1p), kill(3p), sigaction(3p), sigaddset(3p), sigdelset(3p),
sigemptyset(3p), sigfillset(3p), sigismember(3p), sigpending(3p),
sigqueue(3p), sigsuspend(3p)
The Base Definitions volume of POSIX.1‐2017, signal.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any
discrepancy between this version and the original IEEE and The
Open Group Standard, the original IEEE and The Open Group
Standard is the referee document. The original Standard can be
obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 PTHREAD_SIGMASK(3P)
Pages that refer to this page: signal.h(0p), exec(3p), sigaction(3p), sigaddset(3p), sigdelset(3p), sigemptyset(3p), sigfillset(3p), sighold(3p), sigismember(3p), siglongjmp(3p), sigpending(3p), sigprocmask(3p), sigsetjmp(3p), sigtimedwait(3p), sigwait(3p)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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