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).
> 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
