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Date: Tue, 07 Aug 2012 12:52:56 +0200
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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To: Oleg Nesterov <oleg@redhat.com>
CC: Ingo Molnar <mingo@elte.hu>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Anton Arapov <anton@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
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        Roland McGrath <roland@hack.frob.com>,
        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
References: <20120803162954.GA19806@redhat.com> <5020E2E4.3090104@linutronix.de>
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On 08/07/2012 11:41 AM, Sebastian Andrzej Siewior wrote:
> On 08/03/2012 06:29 PM, Oleg Nesterov wrote:
> For uprobes we never set the bit, we only need it cleared. We get here
> via int 3 and do_debug() already clears TIF_BLOCKSTEP because the
> CPU clears the bit in CPU. So both, TIF_BLOCKSTEP and DEBUGCTLMSR_BTF
> are never set.

Actually I'm, wrong. Syscalls do clear the DEBUGCTLMSR_BTF bit, int3
does not. So yes, we need it after all…

Sebastian