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From: =?utf-8?Q?Llu=C3=ADs_Vilanova?= <vilanova@ac.upc.edu>
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Date: Wed, 18 Jan 2017 00:35:29 +0100
In-Reply-To: <20170117094631.GA4265@stefanha-x1.localdomain> (Stefan
	Hajnoczi's message of "Tue, 17 Jan 2017 09:46:31 +0000")
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Subject: Re: [Qemu-devel] [PATCH v4 3/6] hypertrace: [*-user] Add QEMU-side
 proxy to "guest_hypertrace" event
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org, Daniel P Berrange <berrange@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>, Eric Blake <eblake@redhat.com>, Riku Voipio <riku.voipio@iki.fi>

Stefan Hajnoczi writes:

> On Mon, Jan 16, 2017 at 06:05:26PM +0100, Llu=C3=ADs Vilanova wrote:
>> Stefan Hajnoczi writes:
>> > On Mon, Dec 26, 2016 at 09:34:54PM +0100, Llu=C3=ADs Vilanova wrote:
[...]
>> >> +
>> >> +    } else {
>> >> +        /* proxy to next handler */
>> >> +        if (segv_next.sa_sigaction !=3D NULL) {
>> >> +            segv_next.sa_sigaction(signum, siginfo, sigctxt);
>> >> +        } else if (segv_next.sa_handler !=3D NULL) {
>> >> +            segv_next.sa_handler(signum);
>> >> +        }
>>=20
>> > Is there a case when no signal handler was installed (i.e. default
>> > action)?
>>=20
>> Yes, before calling hypertrace_init() or if it is called without a
>> "hypertrace_base" argument set (i.e., the user has not enabled hypertrac=
e in the
>> command line).

> I meant "what happens if !segv_next.sa_action &&
> !segv_next.sa_handler?".  The default signal disposition should take
> effect.  This code is ignoring that case, turning everything into
> SIG_IGN but there is also SIG_DFL.

I see, I didn't take SIG_DFL and SIG_IGN into account, and if both are null=
 (no
handler was installed by the user), I should cleanup my handler and raise()=
 the
signal again to let it go through its default system action.

Sorry for the overall messy patch.


Thanks,
  Lluis