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Date: Tue, 7 Aug 2012 17:12:11 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Anton Arapov <anton@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Roland McGrath <roland@hack.frob.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] ptrace: fix
	set_task_blockstep()->update_debugctlmsr() logic
Message-ID: <20120807151211.GA13390@redhat.com>
References: <20120803162912.GA19767@redhat.com> <20120803162954.GA19806@redhat.com>
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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.