From owner-freebsd-hackers@FreeBSD.ORG Sun Jul 11 21:30:02 2010 Return-Path: Delivered-To: hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id BA60A106566C for ; Sun, 11 Jul 2010 21:30:02 +0000 (UTC) (envelope-from yanegomi@gmail.com) Received: from mail-iw0-f182.google.com (mail-iw0-f182.google.com [209.85.214.182]) by mx1.freebsd.org (Postfix) with ESMTP id 7B1118FC1D for ; Sun, 11 Jul 2010 21:30:02 +0000 (UTC) Received: by iwn35 with SMTP id 35so4990407iwn.13 for ; Sun, 11 Jul 2010 14:30:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=a6oJyMIfQ6peHeDhff0l4JNEAMQMHIuI81K6/biAO90=; b=M5HPGlBrEtI8bSeQuFhVbLgnHXPM3RbbbL4jHgohS+mR3fSlzQRWUhhqdk40SnP8Uv OgJBwxeI8o29NBvblPcL/2gtEAhE/XlBML11WP9+HqwAyDL5FxKFPIcfwn6tRCJZ7uTh l3Bod57HJzN6gwcm/+7FRbaPz/tzagbnzj0f0= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=UjKdIh7Iybr18mBbS0aWaFfoLtJjxLfRGe+/BpmSs5CB1fJyEIE+2ggQ9z7HC/VJ1p DA1xmpyEY7v+lPWUC+KPQZNou55ieAE40CfQl6x9HG7jI0iZAwo1xWTS4HcDDKvNxs1U CLOO6pgxG+Scg/ctouXfcinal1Oihysw8VYls= MIME-Version: 1.0 Received: by 10.231.150.18 with SMTP id w18mr13999196ibv.43.1278883801825; Sun, 11 Jul 2010 14:30:01 -0700 (PDT) Received: by 10.231.192.147 with HTTP; Sun, 11 Jul 2010 14:30:01 -0700 (PDT) In-Reply-To: <20100711210843.GQ2408@deviant.kiev.zoral.com.ua> References: <20100711210843.GQ2408@deviant.kiev.zoral.com.ua> Date: Sun, 11 Jul 2010 14:30:01 -0700 Message-ID: From: Garrett Cooper To: Kostik Belousov Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: hackers@freebsd.org Subject: Re: *sigpause hanging on 8.x+ X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 11 Jul 2010 21:30:02 -0000 On Sun, Jul 11, 2010 at 2:08 PM, Kostik Belousov wrot= e: > 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 com= es up: >> >> $ env LD_LIBRARY_PATH=3D$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 =A0amd64 >> VM: >> FreeBSD starr-bastion.localdomain 8.0-STABLE FreeBSD 8.0-STABLE #0 >> r207913: Tue May 11 06:21:57 UTC 2010 >> root@starr-bastion.localdomain:/usr/obj/usr/src/sys/GENERIC =A0i386 >> >> Index: compat-43/sigcompat.c >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >> --- compat-43/sigcompat.c =A0 =A0 (revision 206173) >> +++ compat-43/sigcompat.c =A0 =A0 (working copy) >> @@ -36,6 +36,7 @@ >> =A0#include "namespace.h" >> =A0#include >> =A0#include >> +#include >> =A0#include >> =A0#include "un-namespace.h" >> =A0#include "libc_private.h" >> @@ -102,7 +103,9 @@ >> =A0{ >> =A0 =A0 =A0 sigset_t set; >> >> + =A0 =A0 printf("before sigemptyset\n"); >> =A0 =A0 =A0 sigemptyset(&set); >> + =A0 =A0 printf("before _sigsuspend\n"); >> =A0 =A0 =A0 set.__bits[0] =3D mask; >> =A0 =A0 =A0 return (_sigsuspend(&set)); >> =A0} >> @@ -111,10 +114,16 @@ >> =A0xsi_sigpause(int sig) >> =A0{ >> =A0 =A0 =A0 sigset_t set; >> + =A0 =A0 int rc; >> >> + =A0 =A0 printf("before sigemptyset\n"); >> =A0 =A0 =A0 sigemptyset(&set); >> + =A0 =A0 printf("before sigaddset\n"); >> =A0 =A0 =A0 sigaddset(&set, sig); >> - =A0 =A0 return (_sigsuspend(&set)); >> + =A0 =A0 printf("before _sigsuspend\n"); >> + =A0 =A0 rc =3D (_sigsuspend(&set)); >> + =A0 =A0 printf("after _sigsuspend\n"); >> + =A0 =A0 return rc; >> =A0} >> >> =A0int >> >> $ cat ~/test_sigpause.c >> #include >> #include >> >> int >> main (void) >> { >> =A0 =A0 =A0 =A0 printf("0\n"); >> =A0 =A0 =A0 =A0 fflush(stdout); >> =A0 =A0 =A0 =A0 (void) sigpause(1); >> =A0 =A0 =A0 =A0 return 0; >> } >> $ cat ~/test_sigsuspend.c >> #include >> #include >> >> int >> main (void) >> { >> =A0 =A0 =A0 =A0 sigset_t oset; >> =A0 =A0 =A0 =A0 sigset_t nset; >> =A0 =A0 =A0 =A0 if (sigprocmask(1, &nset, &oset) =3D=3D -1) >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 err(1, "sigprocmask(-1, &nset, &oset)"); >> =A0 =A0 =A0 =A0 if (sigprocmask(-1, &nset, &oset) =3D=3D -1) >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 err(1, "sigprocmask(-1, &nset, &oset)"); >> =A0 =A0 =A0 =A0 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 eit= her. > diff --git a/lib/libc/compat-43/sigcompat.c b/lib/libc/compat-43/sigcompa= t.c > index c3ba30a..bab9d5c 100644 > --- a/lib/libc/compat-43/sigcompat.c > +++ b/lib/libc/compat-43/sigcompat.c > @@ -111,9 +111,12 @@ int > =A0xsi_sigpause(int sig) > =A0{ > =A0 =A0 =A0 =A0sigset_t set; > + =A0 =A0 =A0 int error; > > - =A0 =A0 =A0 sigemptyset(&set); > - =A0 =A0 =A0 sigaddset(&set, sig); > + =A0 =A0 =A0 error =3D _sigprocmask(SIG_BLOCK, NULL, &set); > + =A0 =A0 =A0 if (error !=3D 0) > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 return (error); > + =A0 =A0 =A0 sigdelset(&set, sig); > =A0 =A0 =A0 =A0return (_sigsuspend(&set)); > =A0} Doesn't this violate the restore clause noted in the manpage? The xsi_sigpause() function removes sig from the signal mask of the ca= ll- 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. 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