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/* Implementation of the POSIX sleep function using nanosleep.
Copyright (C) 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
see <http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <time.h>
#include <signal.h>
#include <unistd.h>
/* version perusing nanosleep */
#if defined __UCLIBC_HAS_REALTIME__
/* I am unable to reproduce alleged "Linux quirk".
* I used the following test program:
#include <unistd.h>
#include <time.h>
#include <signal.h>
static void dummy(int sig) {}
int main() {
struct timespec t = { 2, 0 };
if (fork() == 0) {
sleep(1);
return 0;
}
signal(SIGCHLD, SIG_DFL); //
signal(SIGCHLD, dummy); // Pick one
signal(SIGCHLD, SIG_IGN); //
nanosleep(&t, &t);
return 0;
}
* Testing on 2.4.20 and on 2.6.35-rc4:
* With SIG_DFL, nanosleep is not interrupted by SIGCHLD. Ok.
* With dummy handler, nanosleep is interrupted by SIGCHLD. Ok.
* With SIG_IGN, nanosleep is NOT interrupted by SIGCHLD.
* It looks like sleep's workaround for SIG_IGN is no longer needed?
* The only emails I can find are from 1998 (!):
* ----------
* Subject: Re: sleep ignore sigchld
* From: Linus Torvalds <torvalds@transmeta.com>
* Date: Mon, 16 Nov 1998 11:02:15 -0800 (PST)
*
* On Mon, 16 Nov 1998, H. J. Lu wrote:
* > That is a kernel bug. SIGCHLD is a special one. Usually it cannot
* > be ignored. [snip...]
*
* No can do.
*
* "nanosleep()" is implemented in a bad way that makes it impossible to
* restart it cleanly. It was done that way because glibc wanted it that way,
* not because it's a good idea. [snip...]
* ----------
* I assume that in the passed twelve+ years, nanosleep got fixed,
* but the hack in sleep to work around broken nanosleep was never removed.
*/
# if 0
/* This is a quick and dirty, but not 100% compliant with
* the stupid SysV SIGCHLD vs. SIG_IGN behaviour. It is
* fine unless you are messing with SIGCHLD... */
unsigned int sleep (unsigned int sec)
{
unsigned int res;
struct timespec ts = { .tv_sec = (long int) seconds, .tv_nsec = 0 };
res = nanosleep(&ts, &ts);
if (res) res = (unsigned int) ts.tv_sec + (ts.tv_nsec >= 500000000L);
return res;
}
# else
/* We are going to use the `nanosleep' syscall of the kernel. But the
kernel does not implement the sstupid SysV SIGCHLD vs. SIG_IGN
behaviour for this syscall. Therefore we have to emulate it here. */
unsigned int sleep (unsigned int seconds)
{
struct timespec ts = { .tv_sec = (long int) seconds, .tv_nsec = 0 };
sigset_t set;
struct sigaction oact;
unsigned int result;
/* This is not necessary but some buggy programs depend on this. */
if (seconds == 0) {
# ifdef CANCELLATION_P
int cancelhandling;
CANCELLATION_P (THREAD_SELF);
# endif
return 0;
}
/* Linux will wake up the system call, nanosleep, when SIGCHLD
arrives even if SIGCHLD is ignored. We have to deal with it
in libc. */
__sigemptyset (&set);
__sigaddset (&set, SIGCHLD);
/* Is SIGCHLD set to SIG_IGN? */
sigaction (SIGCHLD, NULL, &oact); /* never fails */
if (oact.sa_handler == SIG_IGN) {
/* Yes. Block SIGCHLD, save old mask. */
sigprocmask (SIG_BLOCK, &set, &set); /* never fails */
}
/* Run nanosleep, with SIGCHLD blocked if SIGCHLD is SIG_IGNed. */
result = nanosleep (&ts, &ts);
if (result != 0) {
/* Got EINTR. Return remaining time. */
result = (unsigned int) ts.tv_sec + (ts.tv_nsec >= 500000000L);
}
if (!__sigismember (&set, SIGCHLD)) {
/* We did block SIGCHLD, and old mask had no SIGCHLD bit.
IOW: we need to unblock SIGCHLD now. Do it. */
/* this sigprocmask call never fails, thus never updates errno,
and therefore we don't need to save/restore it. */
sigprocmask (SIG_SETMASK, &set, NULL); /* never fails */
}
return result;
}
# endif
#else /* __UCLIBC_HAS_REALTIME__ */
/* no nanosleep, use signals and alarm() */
static void sleep_alarm_handler(int attribute_unused sig)
{
}
unsigned int sleep (unsigned int seconds)
{
struct sigaction act, oact;
sigset_t set, oset;
unsigned int result, remaining;
time_t before, after;
int old_errno = errno;
/* This is not necessary but some buggy programs depend on this. */
if (seconds == 0)
return 0;
/* block SIGALRM */
__sigemptyset (&set);
__sigaddset (&set, SIGALRM);
sigprocmask (SIG_BLOCK, &set, &oset); /* can't fail */
act.sa_handler = sleep_alarm_handler;
act.sa_flags = 0;
act.sa_mask = oset;
sigaction(SIGALRM, &act, &oact); /* never fails */
before = time(NULL);
remaining = alarm(seconds);
if (remaining && remaining > seconds) {
/* restore user's alarm */
sigaction(SIGALRM, &oact, NULL);
alarm(remaining); /* restore old alarm */
sigsuspend(&oset);
after = time(NULL);
} else {
sigsuspend (&oset);
after = time(NULL);
sigaction (SIGALRM, &oact, NULL);
}
result = after - before;
alarm(remaining > result ? remaining - result : 0);
sigprocmask (SIG_SETMASK, &oset, NULL);
__set_errno(old_errno);
return result > seconds ? 0 : seconds - result;
}
#endif /* __UCLIBC_HAS_REALTIME__ */
libc_hidden_def(sleep)
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