*sigpause hanging on 8.x+

[Kostik Belousov]

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
> root at starr-bastion.localdomain:/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().

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));
 }
 
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