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SIGWAITINFO(2) Linux Programmer's Manual SIGWAITINFO(2)
sigwaitinfo, sigtimedwait - synchronously wait for queued signals
#include <signal.h>
int sigwaitinfo(const sigset_t *set, siginfo_t *info);
int sigtimedwait(const sigset_t *set, siginfo_t *info,
const struct timespec *timeout);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sigwaitinfo(), sigtimedwait(): _POSIX_C_SOURCE >= 199309L
sigwaitinfo() suspends execution of the calling thread until one of the
signals in set is delivered. (If one of the signals in set is already pending
for the calling thread, sigwaitinfo() will return immediately with information
about that signal.)
sigwaitinfo() removes the delivered signal from the set of pending signals and
returns the signal number as its function result. If the info argument is not
NULL, then it returns a structure of type siginfo_t (see sigaction(2))
containing information about the signal.
Signals returned via sigwaitinfo() are delivered in the usual order; see
signal(7) for further details.
sigtimedwait() operates in exactly the same way as sigwaitinfo() except that
it has an additional argument, timeout, which enables an upper bound to be
placed on the time for which the thread is suspended. This argument is of the
following type:
struct timespec {
long tv_sec; /* seconds */
long tv_nsec; /* nanoseconds */
}
If both fields of this structure are specified as 0, a poll is performed:
sigtimedwait() returns immediately, either with information about a signal
that was pending for the caller, or with an error if none of the signals in
set was pending.
On success, both sigwaitinfo() and sigtimedwait() return a signal number
(i.e., a value greater than zero). On failure both calls return -1, with
errno set to indicate the error.
EAGAIN No signal in set was delivered within the timeout period specified to
sigtimedwait().
EINTR The wait was interrupted by a signal handler; see signal(7). (This
handler was for a signal other than one of those in set.)
EINVAL timeout was invalid.
POSIX.1-2001.
In normal usage, the calling program blocks the signals in set via a prior
call to sigprocmask(2) (so that the default disposition for these signals does
not occur if they are delivered between successive calls to sigwaitinfo() or
sigtimedwait()) and does not establish handlers for these signals. In a
multithreaded program, the signal should be blocked in all threads to prevent
the signal being delivered to a thread other than the one calling
sigwaitinfo() or sigtimedwait()).
The set of signals that is pending for a given thread is the union of the set
of signals that is pending specifically for that thread and the set of signals
that is pending for the process as a whole (see signal(7)).
If multiple threads of a process are blocked waiting for the same signal(s) in
sigwaitinfo() or sigtimedwait(), then exactly one of the threads will actually
receive the signal if it is delivered to the process as a whole; which of the
threads receives the signal is indeterminate.
POSIX leaves the meaning of a NULL value for the timeout argument of
sigtimedwait() unspecified, permitting the possibility that this has the same
meaning as a call to sigwaitinfo(), and indeed this is what is done on Linux.
On Linux, sigwaitinfo() is a library function implemented on top of
sigtimedwait().
kill(2), sigaction(2), signal(2), signalfd(2), sigpending(2), sigprocmask(2),
sigqueue(2), sigsetops(3), sigwait(3), signal(7), time(7)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-10-04 SIGWAITINFO(2)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface