Name
sigprocmask, rt_sigprocmask — examine and change blocked signals
Synopsis
#include <signal.h> /* Prototype for the glibc wrapper function */
int
sigprocmask( |
int how, |
| const sigset_t *restrict set, | |
sigset_t *restrict oldset); |
/* Prototype for the underlying system call */
int
rt_sigprocmask( |
int how, |
| const kernel_sigset_t *set, | |
| kernel_sigset_t *oldset, | |
size_t sigsetsize); |
/* Prototype for the legacy system call (deprecated) */
int
sigprocmask( |
int how, |
| const old_kernel_sigset_t *set, | |
old_kernel_sigset_t *oldset); |
![[Note]](../stylesheet/note.png) |
Note | ||
|---|---|---|---|
|
DESCRIPTION
sigprocmask() is used to
fetch and/or change the signal mask of the calling thread.
The signal mask is the set of signals whose delivery is
currently blocked for the caller (see also signal(7) for more
details).
The behavior of the call is dependent on the value of
how, as follows.
SIG_BLOCK-
The set of blocked signals is the union of the current set and the
setargument. SIG_UNBLOCK-
The signals in
setare removed from the current set of blocked signals. It is permissible to attempt to unblock a signal which is not blocked. SIG_SETMASK-
The set of blocked signals is set to the argument
set.
If oldset is
non-NULL, the previous value of the signal mask is stored in
oldset.
If set is NULL,
then the signal mask is unchanged (i.e., how is ignored), but the
current value of the signal mask is nevertheless returned in
oldset (if it is not
NULL).
A set of functions for modifying and inspecting variables of type sigset_t ("signal sets") is described in sigsetops(3).
The use of sigprocmask() is
unspecified in a multithreaded process; see pthread_sigmask(3).
RETURN VALUE
sigprocmask() returns 0 on
success. On failure, −1 is returned and errno is set to indicate the error.
ERRORS
- EFAULT
-
The
setoroldsetargument points outside the process's allocated address space. - EINVAL
-
Either the value specified in
howwas invalid or the kernel does not support the size passed insigsetsize.
NOTES
It is not possible to block SIGKILL or SIGSTOP. Attempts to do so are silently
ignored.
Each of the threads in a process has its own signal mask.
A child created via fork(2) inherits a copy of its parent's signal mask; the signal mask is preserved across execve(2).
If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are generated while they are
blocked, the result is undefined, unless the signal was
generated by kill(2), sigqueue(3), or raise(3).
See sigsetops(3) for details on manipulating signal sets.
Note that it is permissible (although not very useful) to
specify both set and
oldset as NULL.
C library/kernel differences
The kernel's definition of sigset_t differs in size from that used by the C library. In this manual page, the former is referred to as kernel_sigset_t (it is nevertheless named sigset_t in the kernel sources).
The glibc wrapper function for sigprocmask() silently ignores attempts
to block the two real-time signals that are used internally
by the NPTL threading implementation. See nptl(7) for details.
The original Linux system call was named sigprocmask(). However, with the addition
of real-time signals in Linux 2.2, the fixed-size, 32-bit
sigset_t (referred to as
old_kernel_sigset_t in this
manual page) type supported by that system call was no
longer fit for purpose. Consequently, a new system call,
rt_sigprocmask(), was added
to support an enlarged sigset_t
type (referred to as kernel_sigset_t in this manual page). The new
system call takes a fourth argument, size_t sigsetsize, which
specifies the size in bytes of the signal sets in
set and oldset. This argument is
currently required to have a fixed architecture specific
value (equal to sizeof(kernel_sigset_t)).
The glibc sigprocmask()
wrapper function hides these details from us, transparently
calling rt_sigprocmask() when
the kernel provides it.
SEE ALSO
kill(2), pause(2), sigaction(2), signal(2), sigpending(2), sigsuspend(2), pthread_sigmask(3), sigqueue(3), sigsetops(3), signal(7)
COLOPHON
This page is part of release 5.11 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (c) 2005 Michael Kerrisk based on earlier work by faithcs.unc.edu and Mike Battersby <mibdeakin.edu.au> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END 2005-09-15, mtk, Created new page by splitting off from sigaction.2 |