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Diffstat (limited to 'man/man2/sigprocmask.2')
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diff --git a/man/man2/sigprocmask.2 b/man/man2/sigprocmask.2 new file mode 100644 index 0000000..47bbc69 --- /dev/null +++ b/man/man2/sigprocmask.2 @@ -0,0 +1,224 @@ +.\" Copyright (c) 2005 Michael Kerrisk +.\" based on earlier work by faith@cs.unc.edu and +.\" Mike Battersby <mib@deakin.edu.au> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" 2005-09-15, mtk, Created new page by splitting off from sigaction.2 +.\" +.TH sigprocmask 2 2024-05-02 "Linux man-pages (unreleased)" +.SH NAME +sigprocmask, rt_sigprocmask \- examine and change blocked signals +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.B #include <signal.h> +.P +.nf +/* Prototype for the glibc wrapper function */ +.BI "int sigprocmask(int " how ", const sigset_t *_Nullable restrict " set , +.BI " sigset_t *_Nullable restrict " oldset ); +.P +.BR "#include <signal.h>" " /* Definition of " SIG_* " constants */" +.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */" +.B #include <unistd.h> +.P +/* Prototype for the underlying system call */ +.BI "int syscall(SYS_rt_sigprocmask, int " how , +.BI " const kernel_sigset_t *_Nullable " set , +.BI " kernel_sigset_t *_Nullable " oldset , +.BI " size_t " sigsetsize ); +.P +/* Prototype for the legacy system call */ +.BI "[[deprecated]] int syscall(SYS_sigprocmask, int " how , +.BI " const old_kernel_sigset_t *_Nullable " set , +.BI " old_kernel_sigset_t *_Nullable " oldset ); +.fi +.P +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.P +.BR sigprocmask (): +.nf + _POSIX_C_SOURCE +.fi +.SH DESCRIPTION +.BR 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 +.BR signal (7) +for more details). +.P +The behavior of the call is dependent on the value of +.IR how , +as follows. +.TP +.B SIG_BLOCK +The set of blocked signals is the union of the current set and the +.I set +argument. +.TP +.B SIG_UNBLOCK +The signals in +.I set +are removed from the current set of blocked signals. +It is permissible to attempt to unblock a signal which is not blocked. +.TP +.B SIG_SETMASK +The set of blocked signals is set to the argument +.IR set . +.P +If +.I oldset +is non-NULL, the previous value of the signal mask is stored in +.IR oldset . +.P +If +.I set +is NULL, then the signal mask is unchanged (i.e., +.I how +is ignored), +but the current value of the signal mask is nevertheless returned in +.I oldset +(if it is not NULL). +.P +A set of functions for modifying and inspecting variables of type +.I sigset_t +("signal sets") is described in +.BR sigsetops (3). +.P +The use of +.BR sigprocmask () +is unspecified in a multithreaded process; see +.BR pthread_sigmask (3). +.SH RETURN VALUE +.BR sigprocmask () +returns 0 on success. +On failure, \-1 is returned and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EFAULT +The +.I set +or +.I oldset +argument points outside the process's allocated address space. +.TP +.B EINVAL +Either the value specified in +.I how +was invalid or the kernel does not support the size passed in +.I sigsetsize. +.SH VERSIONS +.SS C library/kernel differences +The kernel's definition of +.I sigset_t +differs in size from that used +by the C library. +In this manual page, the former is referred to as +.I kernel_sigset_t +(it is nevertheless named +.I sigset_t +in the kernel sources). +.P +The glibc wrapper function for +.BR sigprocmask () +silently ignores attempts to block the two real-time signals that +are used internally by the NPTL threading implementation. +See +.BR nptl (7) +for details. +.P +The original Linux system call was named +.BR sigprocmask (). +However, with the addition of real-time signals in Linux 2.2, +the fixed-size, 32-bit +.I sigset_t +(referred to as +.I 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, +.BR rt_sigprocmask (), +was added to support an enlarged +.I sigset_t +type +(referred to as +.I kernel_sigset_t +in this manual page). +The new system call takes a fourth argument, +.IR "size_t sigsetsize" , +which specifies the size in bytes of the signal sets in +.I set +and +.IR oldset . +This argument is currently required to have a fixed architecture specific value +(equal to +.IR sizeof(kernel_sigset_t) ). +.\" sizeof(kernel_sigset_t) == _NSIG / 8, +.\" which equals to 8 on most architectures, but e.g. on MIPS it's 16. +.P +The glibc +.BR sigprocmask () +wrapper function hides these details from us, transparently calling +.BR rt_sigprocmask () +when the kernel provides it. +.\" +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +POSIX.1-2001. +.SH NOTES +It is not possible to block +.BR SIGKILL " or " SIGSTOP . +Attempts to do so are silently ignored. +.P +Each of the threads in a process has its own signal mask. +.P +A child created via +.BR fork (2) +inherits a copy of its parent's signal mask; +the signal mask is preserved across +.BR execve (2). +.P +If +.BR SIGBUS , +.BR SIGFPE , +.BR SIGILL , +or +.B SIGSEGV +are generated +while they are blocked, the result is undefined, +unless the signal was generated by +.BR kill (2), +.BR sigqueue (3), +or +.BR raise (3). +.P +See +.BR sigsetops (3) +for details on manipulating signal sets. +.P +Note that it is permissible (although not very useful) to specify both +.I set +and +.I oldset +as NULL. +.SH SEE ALSO +.BR kill (2), +.BR pause (2), +.BR sigaction (2), +.BR signal (2), +.BR sigpending (2), +.BR sigsuspend (2), +.BR pthread_sigmask (3), +.BR sigqueue (3), +.BR sigsetops (3), +.BR signal (7) |