On Wed, Feb 24, 2010 at 03:09:54PM +0000, Richard W.M. Jones wrote: > On Wed, Feb 24, 2010 at 03:39:20PM +0100, Paolo Bonzini wrote: > > On 02/24/2010 02:06 PM, Richard W.M. Jones wrote: > >> The correct solution is to mask out SIGWINCH for the duration > >> of the poll(2) system call. The per-thread mask is changed and > >> restored immediately after the call. Since we are using > >> pthread_sigmask, this should not affect other threads, and > >> since we restore the signal mask immediately afterwards it should > >> not affect the current thread visibly either. > > > > This is interesting. No signal handler will necessarily do things like > > longjmp-ing out of the remote driver, so every signal could give rise to > > a similar bug. > > Did you mean "signals handlers might longjmp out ..."? I've seen a > few in my time that have done that. I notice the top Google hit for > "signal handler" & "longjmp" is this warning about the practice from > CERT: > > https://www.securecoding.cert.org/confluence/display/seccode/SIG32-C.+Do+not+call+longjmp%28%29+from+inside+a+signal+handler > > > In particular, SIGCHLD would be an obvious candidate for being handled > > the same way, since both SIGWINCH and SIGCHLD are default-ignored > > signals. On the other hand, while for SIGWINCH it would be mostly > > harmless(*), for SIGCHLD it would leave a zombie until the remote > > libvirtd answers. Any ideas? > > > > (*) Unless you have more than one thread using curses, and a thread > > other than the one calling libvirt has blocked SIGWINCH. > > Certainly SIGCHLD could be added. I was keeping this patch minimal so > it just fixes the problem I observed, to reduce the chance that a > change to such a critical piece of code could break anything else. I think SIGWINCH + SIGCHLD + SIGPIPE are a reasonably set to block since those are common "normal" signals a process may received during operation. Other signals are all typically related to fatal problems rather tha normal conditions Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list