This is the mail archive of the
libc-hacker@sourceware.cygnus.com
mailing list for the glibc project.
Re: A patch for nanosleep
- To: zack@rabi.columbia.edu (Zack Weinberg)
- Subject: Re: A patch for nanosleep
- From: hjl@lucon.org (H.J. Lu)
- Date: Tue, 17 Nov 1998 10:36:57 -0800 (PST)
- Cc: libc-hacker@cygnus.com, torvalds@transmeta.com (Linus Torvalds), linux-kernel@vger.rutgers.edu (linux kernel)
>
> On Tue, 17 Nov 1998 09:29:20 -0800 (PST), H.J. Lu wrote:
> >
> >Here is an optimized nanosleep.c for glibc 2.
>
> [...]
>
> > /* Should we really block SIGCHLD? */
> > ignored = (oact.sa_handler == SIG_IGN);
> >
> > if (!ignored)
> > /* Restore the original signal mask. */
> > (void) sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
> >
> > ret = __syscall_nanosleep (req, rem);
> >
> > if (ignored)
>
> These 'if' conditions are backward.
>
I don't think so. If SIGCHLD is ignored, we have to block SIGCHLD in
nanosleep. Otherwise, we have to restore the original signal mask.
Here is an update. I hope it is easier to understand.
--
H.J. Lu (hjl@gnu.org)
----
/* Copyright (C) 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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 <signal.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
extern int __syscall_nanosleep (const struct timespec *req,
struct timespec *rem);
int
__nanosleep(const struct timespec *req, struct timespec *rem)
{
sigset_t set, oset;
struct sigaction oact;
int saved_errno;
int ret;
/* Linux will wake up the system call, nanosleep, when SIGCHLD
arrives even if SIGCHLD is ignored. We have to deal with it
in libc. We block SIGCHLD first. */
if (sigemptyset (&set) < 0 ||
sigaddset (&set, SIGCHLD) < 0 ||
sigprocmask (SIG_BLOCK, &set, &oset))
return -1;
/* If SIGCHLD is already blocked, we don't have to do anything. */
if (!sigismember (&oset, SIGCHLD))
{
/* We get the signal handler for SIGCHLD. */
if (sigaction (SIGCHLD, (struct sigaction *) NULL, &oact) < 0)
{
saved_errno = errno;
/* Restore the original signal mask. */
(void) sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
__set_errno (saved_errno);
return -1;
}
if (oact.sa_handler == SIG_IGN)
{
/* We should leave SIGCHLD blocked. */
ret = __syscall_nanosleep (req, rem);
saved_errno = errno;
/* Restore the original signal mask. */
(void) sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
__set_errno (saved_errno);
}
else
{
/* We should unblock SIGCHLD. Restore the original signal
mask. */
(void) sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
ret = __syscall_nanosleep (req, rem);
}
}
else
ret = __syscall_nanosleep (req, rem);
return ret;
}
weak_alias (__nanosleep, nanosleep)