On Sun, Jul 11, 2010 at 02:30:01PM -0700, Garrett Cooper wrote: > On Sun, Jul 11, 2010 at 2:08 PM, Kostik Belousov <[email protected]> wrote: > > On Sun, Jul 11, 2010 at 12:39:39PM -0700, Garrett Cooper wrote: > >> So, long story short... I've basically ported the open posix testsuite > >> to FreeBSD, and one of the tests tests out sigpause. Unfortunately the > >> sucker hangs on my dev box at home. > >> > >> I've written a short testcase that demonstrates this. It prints out: > >> > >> $ ~/test_sigpause > >> 0 > >> > >> And proceeds to be unresponsive to signals (except SIGSTOP / SIGKILL, > >> as expected). > >> > >> When I monkey around with libc's compat4.3 stuff a bit, this is what comes > >> up: > >> > >> $ env LD_LIBRARY_PATH=$PWD:/usr/src/lib/libc/../libthr ~/test_sigpause > >> 0 > >> before sigemptyset > >> before _sigsuspend > >> > >> So it's getting stuck after calling _sigsuspend. > >> > >> I tried the same thing on a i386 8-STABLE VM and it hangs as well. > >> > >> I tried applying similar printfs in libthr but it's not hitting that > >> code at all (it's now responding to SIGTERM though, which is > >> interesting, but not too interesting to me). > >> > >> I also wrote similar code that exercised the functionality in > >> sigsuspend, by calling sigprocmask beforehand, and it works. > >> > >> Thoughts? > >> > >> -Garrett > >> > >> Dev machine: > >> FreeBSD bayonetta.local 9.0-CURRENT FreeBSD 9.0-CURRENT #1 > >> r206173:209901M: Sun Jul 11 04:18:42 PDT 2010 > >> root@:/usr/obj/usr/src/sys/BAYONETTA amd64 > >> VM: > >> FreeBSD starr-bastion.localdomain 8.0-STABLE FreeBSD 8.0-STABLE #0 > >> r207913: Tue May 11 06:21:57 UTC 2010 > >> [email protected]:/usr/obj/usr/src/sys/GENERIC i386 > >> > >> Index: compat-43/sigcompat.c > >> =================================================================== > >> --- compat-43/sigcompat.c (revision 206173) > >> +++ compat-43/sigcompat.c (working copy) > >> @@ -36,6 +36,7 @@ > >> #include "namespace.h" > >> #include <sys/param.h> > >> #include <signal.h> > >> +#include <stdio.h> > >> #include <string.h> > >> #include "un-namespace.h" > >> #include "libc_private.h" > >> @@ -102,7 +103,9 @@ > >> { > >> sigset_t set; > >> > >> + printf("before sigemptyset\n"); > >> sigemptyset(&set); > >> + printf("before _sigsuspend\n"); > >> set.__bits[0] = mask; > >> return (_sigsuspend(&set)); > >> } > >> @@ -111,10 +114,16 @@ > >> xsi_sigpause(int sig) > >> { > >> sigset_t set; > >> + int rc; > >> > >> + printf("before sigemptyset\n"); > >> sigemptyset(&set); > >> + printf("before sigaddset\n"); > >> sigaddset(&set, sig); > >> - return (_sigsuspend(&set)); > >> + printf("before _sigsuspend\n"); > >> + rc = (_sigsuspend(&set)); > >> + printf("after _sigsuspend\n"); > >> + return rc; > >> } > >> > >> int > >> > >> $ cat ~/test_sigpause.c > >> #include <signal.h> > >> #include <stdio.h> > >> > >> int > >> main (void) > >> { > >> printf("0\n"); > >> fflush(stdout); > >> (void) sigpause(1); > >> return 0; > >> } > >> $ cat ~/test_sigsuspend.c > >> #include <err.h> > >> #include <signal.h> > >> > >> int > >> main (void) > >> { > >> sigset_t oset; > >> sigset_t nset; > >> if (sigprocmask(1, &nset, &oset) == -1) > >> err(1, "sigprocmask(-1, &nset, &oset)"); > >> if (sigprocmask(-1, &nset, &oset) == -1) > >> err(1, "sigprocmask(-1, &nset, &oset)"); > >> return (sigsuspend(&nset)); > >> } > > > > It seems I got a sigmask for sigpause inside the xsi_sigpause() backward. > > On the other hand, I do not understand what is your issue with sigpause(). > > The negative testcase from the open posix testsuite was setup so that > setting sigpause(-1) would return -1 with EINVAL, according to the > sig* manpages (-1 is an invalid signal of course). That isn't being > triggered with either function today. > > 0 seems a bit wonky too (it's an invalid signal number). > > My bet is that values greater than SIGRTMAX aren't interpreted properly > either. I will add these checks, thanks.
>
> > diff --git a/lib/libc/compat-43/sigcompat.c b/lib/libc/compat-43/sigcompat.c
> > index c3ba30a..bab9d5c 100644
> > --- a/lib/libc/compat-43/sigcompat.c
> > +++ b/lib/libc/compat-43/sigcompat.c
> > @@ -111,9 +111,12 @@ int
> > xsi_sigpause(int sig)
> > {
> > sigset_t set;
> > + int error;
> >
> > - sigemptyset(&set);
> > - sigaddset(&set, sig);
> > + error = _sigprocmask(SIG_BLOCK, NULL, &set);
> > + if (error != 0)
> > + return (error);
> > + sigdelset(&set, sig);
> > return (_sigsuspend(&set));
> > }
>
> Doesn't this violate the restore clause noted in the manpage?
>
> The xsi_sigpause() function removes sig from the signal mask of the call-
> ing process and suspend the calling process until a signal is received.
> The xsi_sigpause() function restores the signal mask of the process to
> its original state before returning.
>
> So if I had a sigset defined above with sig, then redefined it, I
> would be whacking the previous handler by passing in NULL to
> _sigprocmask, correct? If so, sigpause has issues too in its
> implementation.
No, not correct. Read the description of sigsuspend. Also note that
the sigprocmask call does not change process mask.
>
> There's also some interesting SIGDELSET action going on in libthr's
> copy of _sigsuspend's with SIGCANCEL (apparently that's the unofficial
> alias for SIGRTMIN as defined by libthr), but that's a sidenote for
> the actual issue seen here.
>
> Thanks!
> -Garrett
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