pthread_sigmask.3p (6968B)
- '\" et
- .TH PTHREAD_SIGMASK "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- 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.
- .\"
- .SH NAME
- pthread_sigmask,
- sigprocmask
- \(em examine and change blocked signals
- .SH SYNOPSIS
- .LP
- .nf
- #include <signal.h>
- .P
- int pthread_sigmask(int \fIhow\fP, const sigset_t *restrict \fIset\fP,
- sigset_t *restrict \fIoset\fP);
- int sigprocmask(int \fIhow\fP, const sigset_t *restrict \fIset\fP,
- sigset_t *restrict \fIoset\fP);
- .fi
- .SH DESCRIPTION
- The
- \fIpthread_sigmask\fR()
- 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
- \fIsigprocmask\fR(),
- without the restriction that the call be made in a single-threaded
- process.
- .P
- In a single-threaded process, the
- \fIsigprocmask\fR()
- function shall examine or change (or both) the signal mask of the
- calling thread.
- .P
- If the argument
- .IR set
- is not a null pointer, it points to a set of signals to be used to
- change the currently blocked set.
- .P
- The argument
- .IR how
- indicates the way in which the set is changed, and the application
- shall ensure it consists of one of the following values:
- .IP SIG_BLOCK 12
- The resulting set shall be the union of the current set and the signal
- set pointed to by
- .IR set .
- .IP SIG_SETMASK 12
- The resulting set shall be the signal set pointed to by
- .IR set .
- .IP SIG_UNBLOCK 12
- The resulting set shall be the intersection of the current set and the
- complement of the signal set pointed to by
- .IR set .
- .P
- If the argument
- .IR oset
- is not a null pointer, the previous mask shall be stored in the location
- pointed to by
- .IR oset .
- If
- .IR set
- is a null pointer, the value of the argument
- .IR 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.
- .P
- If there are any pending unblocked signals after the call to
- \fIsigprocmask\fR(),
- at least one of those signals shall be delivered before the call to
- \fIsigprocmask\fR()
- returns.
- .P
- 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.
- .P
- 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
- \fIkill\fR(),
- \fIpthread_kill\fR(),
- \fIraise\fR(),
- or
- \fIsigqueue\fR().
- .P
- If
- \fIsigprocmask\fR()
- fails, the thread's signal mask shall not be changed.
- .P
- The use of the
- \fIsigprocmask\fR()
- function is unspecified in a multi-threaded process.
- .SH "RETURN VALUE"
- Upon successful completion
- \fIpthread_sigmask\fR()
- shall return 0; otherwise, it shall return the corresponding error
- number.
- .P
- Upon successful completion,
- \fIsigprocmask\fR()
- shall return 0; otherwise, \-1 shall be returned,
- .IR errno
- shall be set to indicate the error, and the signal mask of the process
- shall be unchanged.
- .SH ERRORS
- The
- \fIpthread_sigmask\fR()
- and
- \fIsigprocmask\fR()
- functions shall fail if:
- .TP
- .BR EINVAL
- The value of the
- .IR how
- argument is not equal to one of the defined values.
- .P
- The
- \fIpthread_sigmask\fR()
- function shall not return an error code of
- .BR [EINTR] .
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- .SS "Signaling in a Multi-Threaded Process"
- .P
- This example shows the use of
- \fIpthread_sigmask\fR()
- in order to deal with signals in a multi-threaded process. It provides
- a fairly general framework that could be easily adapted/extended.
- .sp
- .RS 4
- .nf
- #include <stdio.h>
- #include <stdlib.h>
- #include <pthread.h>
- #include <signal.h>
- #include <string.h>
- #include <errno.h>
- \&...
- .P
- static sigset_t signal_mask; /* signals to block */
- .P
- int main (int argc, char *argv[])
- {
- pthread_t sig_thr_id; /* signal handler thread ID */
- int rc; /* return code */
- .P
- 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 */
- .P
- rc = pthread_create (&sig_thr_id, NULL, signal_thread, NULL);
- if (rc != 0) {
- /* handle error */
- ...
- }
- .P
- /* APPLICATION CODE */
- ...
- }
- .P
- void *signal_thread (void *arg)
- {
- int sig_caught; /* signal caught */
- int rc; /* returned code */
- .P
- 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, "\enUnexpected signal %d\en", sig_caught);
- break;
- }
- }
- .fi
- .P
- .RE
- .SH "APPLICATION USAGE"
- None.
- .SH RATIONALE
- When a thread's signal mask is changed in a signal-catching function
- that is installed by
- \fIsigaction\fR(),
- the restoration of the signal mask on return from the signal-catching
- function overrides that change (see
- \fIsigaction\fR()).
- If the signal-catching function was installed with
- \fIsignal\fR(),
- it is unspecified whether this occurs.
- .P
- See
- \fIkill\fR()
- for a discussion of the requirement on delivery of signals.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "\fIexec\fR\^",
- .IR "\fIkill\fR\^(\|)",
- .IR "\fIsigaction\fR\^(\|)",
- .IR "\fIsigaddset\fR\^(\|)",
- .IR "\fIsigdelset\fR\^(\|)",
- .IR "\fIsigemptyset\fR\^(\|)",
- .IR "\fIsigfillset\fR\^(\|)",
- .IR "\fIsigismember\fR\^(\|)",
- .IR "\fIsigpending\fR\^(\|)",
- .IR "\fIsigqueue\fR\^(\|)",
- .IR "\fIsigsuspend\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "\fB<signal.h>\fP"
- .\"
- .SH COPYRIGHT
- 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 .
- .PP
- 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 .