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From: Roland McGrath <roland@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       linux-arch@vger.kernel.org
Subject: Re: [PATCH] ptrace: copy_thread() should clear TIF_SINGLESTEP and
	X86_EFLAGS_TF
In-Reply-To: Oleg Nesterov's message of  Friday, 6 November 2009 22:50:04 +0100 <20091106215004.GA2232@redhat.com>
References: <20091106211637.GA1696@redhat.com>
	<20091106212554.BD731CF@magilla.sf.frob.com>
	<20091106215004.GA2232@redhat.com>
Message-Id: <20091106221002.8057DCF@magilla.sf.frob.com>
Date: Fri,  6 Nov 2009 14:10:02 -0800 (PST)
Sender: linux-kernel-owner@vger.kernel.org
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> I thought this flag has no effect without TIF_SINGLESTEP, and it is
> always updated by enable_single_step().

Right, but to be anal about the semantics you shouldn't clear TF if it's
not set, etc.

> user_disable_single_step() is very much arch-dependent, I am worried
> if it is safe to call it from copy_process(), when the new task_struct,
> thread_info, etc are not properly initialized yet...

Well, arch people can weigh in about if it is problematical.
Skimming over the existing arch definitions, it looks OK to me.


Thanks,
Roland
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