The following reply was made to PR port-sparc64/29824; it has been noted by GNATS.

From: Chuck Silvers <chuq@chuq.com>
To: Matthias Scheler <tron@zhadum.de>
Cc: port-sparc64-maintainer@netbsd.org, xsrc-manager@netbsd.org,
	netbsd-bugs@netbsd.org, NetBSD GNATS <gnats-bugs@netbsd.org>,
	macallan18@earthlink.net
Subject: Re: port-sparc64/29824
Date: Mon, 2 May 2005 08:06:04 -0700

 On Sun, May 01, 2005 at 10:44:20PM +0100, Matthias Scheler wrote:
 > On Sun, May 01, 2005 at 02:37:17PM -0700, Chuck Silvers wrote:
 > > > Responsible-Changed-From-To: xsrc-manager->port-sparc64-maintainer
 > > > Responsible-Changed-By: tron@netbsd.org
 > > > Responsible-Changed-When: Sun, 01 May 2005 18:14:03 +0000
 > > > Responsible-Changed-Why:
 > > > 1.) XFree86's signal handling code does *not* cause this. It will not
 > > >     unblock SIGIO from a the SIGIO signal handler.
 > > 
 > > I just read the code again, it sure looks like it does to me.
 > > the call stack in the initial PR comments looks like it could really happen.
 > 
 > How?
 
 sorry, I misread your comment.  you're right that it does not unblock
 SIGIO in the SIGIO handler, but that's not the problem.  just calling
 sigprocmask() in a signal handler is not safe, at least with our pthreads
 implementation.   I looked briefly for any mention in our manpages of
 what library functions are or are not safe to call in a signal handler,
 but I didn't find it.
 
 -Chuck
 
 
 > 1.) xf86BlockSIGIO() returns whether the signal has been blocked before:
 > 
 > int
 > xf86BlockSIGIO (void)
 > {
 >     sigset_t    set, old;
 > 
 >     sigemptyset (&set);
 >     sigaddset (&set, SIGIO);
 >     sigprocmask (SIG_BLOCK, &set, &old);
 >     return sigismember (&old, SIGIO);
 > }
 > 
 > 2.) xf86SigioReadInput() remembers that flag and passed it to
 >     xf86UnblockSIGIO():
 > 
 > static void
 > xf86SigioReadInput(int fd,
 >                    void *closure)
 > {
 >     int sigstate = xf86BlockSIGIO();
 > [...]
 >     xf86UnblockSIGIO(sigstate);
 > }
 > 
 > 3.) void xf86UnblockSIGIO() only unblocks the signal if it has not been
 >     blocked before:
 > 
 > void
 > xf86UnblockSIGIO (int wasset)
 > {
 >     sigset_t    set;
 > 
 >     if (!wasset)
 >     {
 >         sigemptyset (&set);
 >         sigaddset (&set, SIGIO);
 >         sigprocmask (SIG_UNBLOCK, &set, NULL);
 >     }
 > }
 > 
 > That looks safe to me.
 > 
 > 	Kind regards
 > 
 > -- 
 > Matthias Scheler                                  http://scheler.de/~matthias/