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From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Fri, 4 Mar 2011 17:41:21 +0100
Message-ID: <AANLkTikk=4ssOYBK8+11ydp+-Y1-B6_wd0yYb6OKcz8Z@mail.gmail.com>
Subject: Re: [RFC] Proposal for ptrace improvements
To: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Tejun Heo <tj@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
        Roland McGrath <roland@redhat.com>, linux-kernel@vger.kernel.org,
        torvalds@linux-foundation.org, akpm@linux-foundation.org
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On Fri, Mar 4, 2011 at 5:14 PM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Tue, 01 Mar 2011 23:14:14 +0100, Denys Vlasenko wrote:
>> On Tue, Mar 1, 2011 at 8:06 PM, Jan Kratochvil <jan.kratochvil@redhat.com> wrote:
>> > Currently it is already a problem that apps did not / do not expect the first
>> > waitpid after PTRACE_ATTACH may not be SIGSTOP.
>>
>> That's exactly why we want to add a better alternative, which doesn't
>> insert that blasted SIGSTOP.
>
> But it inserts blasted SIGTRAP (or some other signal) instead.

Not a problem. The problem with SIGSTOP is that we race against
possible real SIGSTOP.

> It would be best if such PTRACE_SEIZE (similar to PTRACE_INTERRUPT)

My understanding is that those are the same idea with different names.

> would
> guarantee the first waitpid afterwards returns the artificial signal from
> PTRACE_SEIZE.

Yes.

-- 
vda
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