/* 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, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #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 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)