linux-kernel - Re: ptrace group stop signal number not reset before PTRACE

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Message-ID: <20160818162311.GA27883@redhat.com>
Date:   Thu, 18 Aug 2016 18:23:11 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Keno Fischer <keno@...iacomputing.com>
Cc:     roland@...k.frob.com, linux-kernel@...r.kernel.org,
        Tejun Heo <tj@...nel.org>
Subject: Re: ptrace group stop signal number not reset before
        PTRACE_INTERRUPT is delivered?

Damn, forgot to mention...

On 08/18, Oleg Nesterov wrote:
>
> Damn. I'll try to think more, but I simply can't decide what do we
> actually want in this case.

Yes, but at least

	> Further, the current behavior seems to make it
	> very hard (impossible?) to reliably tell a true group-stop from a
	> PTRACE_INTERRUPT generated one.

is not true or I misunderstood... PTRACE_INTERRUPT doesn't lead to
group-stop, it stops the tracee individually.

And you if you get PTRACE_EVENT_STOP and WSTOPSIG() == SIGTTIN after
PTRACE_INTERRUPT, you know that the tracee did not report the "new"
SIGTTIN.

Or I missed your point?

Oleg.