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Date: Fri, 20 May 2011 11:12:56 +0200
From: Tejun Heo <tj@kernel.org>
To: Pedro Alves <pedro@codesourcery.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>, oleg@redhat.com,
        jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org,
        torvalds@linux-foundation.org, akpm@linux-foundation.org, indan@nul.nu,
        bdonlan@gmail.com
Subject: Re: [PATCH 03/10] ptrace: implement PTRACE_SEIZE
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 <201105200000.18310.pedro@codesourcery.com>
 <201105200344.44520.vda.linux@googlemail.com>
 <201105200956.23320.pedro@codesourcery.com>
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Hello,

On Fri, May 20, 2011 at 09:56:22AM +0100, Pedro Alves wrote:
> > Ptrace API never allowed poking of running tracees.
> 
> Which is a bit lame.

Lame as it may be, it would be quite challenging to change that.

> > You need to stop it first.
> 
> That was my point...  I was just pointing out that GDB will end
> up PTRACE_INTERRUPTing the target anyway.  Maybe we could extend
> GDB's "observer" mode to be even more observer-only, and delay
> reading the DSO list and whatever else GDB does on attach until
> the first stop, or to user request.  Some archs need reading
> registers as soon as possible in order to actually know which
> arch variant we've attached to.  Anyway, this is GDBs business.
> SEIZE not interrupting won't hurt GDB, and is obviously useful for
> some use cases and tracers, _provided the race with SETOPTS is fixed_.

Other than the to-be-removed SIGTRAP, I don't think the trace is
observable from userland.  Do you have anything specific on mind?

Thanks.

-- 
tejun
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