linux-kernel - Re: [PATCH 2/2] ptrace: fix set_task_blockstep()->update

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Message-ID: <20120807151211.GA13390@redhat.com>
Date:	Tue, 7 Aug 2012 17:12:11 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Roland McGrath <roland@...k.frob.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ptrace: fix
	set_task_blockstep()->update_debugctlmsr() logic

Hi.

Today I noticed by accident that starting from Aug 4 (at least)
all my emails went to nowhere. I am resending some of them...


On 08/03, Oleg Nesterov wrote:
>
> 2. It is wrong. The state of DEBUGCTLMSR_BTF bit in CPU register
>    should always match the state of current's TIF_BLOCKSTEP bit.

Yes.

But this means we should set/clear TIF_BLOCKSTEP and update
MSR_IA32_DEBUGCTLMSR "atomically" under preempt_disable().

I'll redo this patch.

Oleg.

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