проверять и изменять заблокированные сигналы (examine and change blocked signals)
Пролог (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.
Имя (Name)
pthread_sigmask, sigprocmask — examine and change blocked signals
Синопсис (Synopsis)
#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);
Описание (Description)
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.
Возвращаемое значение (Return value)
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.
Ошибки (Error)
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.
Примеры (Examples)
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;
}
}
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
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.
Будущие направления (Future directions)
None.
Смотри также (See also)
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)
