On Wed, Oct 09, 2013 at 10:05:44AM +0200, Paolo Bonzini wrote:
> Il 08/10/2013 23:51, Marcelo Tosatti ha scritto:
> > On Tue, Oct 08, 2013 at 10:03:48AM +0200, Paolo Bonzini wrote:
> >> Il 08/10/2013 02:41, Marcelo Tosatti ha scritto:
> >>> + /* unblock SIGBUS */
> >>> + pthread_sigmask(SIG_BLOCK, NULL, &oldset);
> >>> + sigemptyset(&set);
> >>> + sigaddset(&set, SIGBUS);
> >>> + pthread_sigmask(SIG_UNBLOCK, &set, NULL);
> >>
> >> Please instead modify qemu-thread-posix.c to unblock all per-thread
> >> signals (SIGBUS, SIGSEGV, SIGILL, SIGFPE and SIGSYS). There is no need
> >> to keep those blocked.
> >
> > main-loop.c handles SIGBUS via signalfd to emulate MCEs (associated
> > commits). Therefore it must be blocked.
>
> How was that tested? For BUS_MCEERR_AO it can work, but BUS_MCEERR_AR
> calls force_sig_info which does this:
>
> ignored = action->sa.sa_handler == SIG_IGN;
> blocked = sigismember(&t->blocked, sig);
> if (blocked || ignored) {
> action->sa.sa_handler = SIG_DFL;
> if (blocked) {
> sigdelset(&t->blocked, sig);
> recalc_sigpending_and_wake(t);
> }
>
> if (action->sa.sa_handler == SIG_DFL)
> t->signal->flags &= ~SIGNAL_UNKILLABLE;
>
> and kills the process (because that's the default action of SIG_DFL).
For vcpu context its not blocked?
> > Note that what this patch does it to maintain the signal handling state
> > (it saves the previous state, modifies state, restores previous state) so
> > that its unchanged.
>
> Yes, understood. I was missing the part about MCE (I knew it used
> SIGBUS, but forgot about signalfd). So this patch is good, but the
> above point about BUS_MCEERR_AR needs to be checked sooner or later.
>
> Paolo
