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From: Roland McGrath <roland@redhat.com>
To: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>, caiqian@redhat.com,
       Heiko Carstens <heiko.carstens@de.ibm.com>,
       Jan Kratochvil <jkratoch@redhat.com>, linux-kernel@vger.kernel.org,
       linux-s390@vger.kernel.org, utrace-devel@redhat.com
Subject: Re: s390 && user_enable_single_step() (Was: odd utrace testing
 results on s390x)
In-Reply-To: Martin Schwidefsky's message of  Tuesday, 5 January 2010 10:26:06 +0100 <20100105102606.4f223990@mschwide.boeblingen.de.ibm.com>
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	<20100104171626.22ea2d9c@mschwide.boeblingen.de.ibm.com>
	<20100104181412.GA21146@redhat.com>
	<20100105102606.4f223990@mschwide.boeblingen.de.ibm.com>
Message-Id: <20100106211536.0F6AC134D@magilla.sf.frob.com>
Date: Wed,  6 Jan 2010 13:15:36 -0800 (PST)
Sender: linux-kernel-owner@vger.kernel.org
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> > then the test-case from 6580807da14c423f0d0a708108e6df6ebc8bc83d
> > fails. This probably means that copy_process()->user_disable_single_step()
> > is not enough to clear the "this task wants single-stepping" copied
> > from parent.
> 
> user_disable_single_step() does not remove the TIF_SINGLE_STEP bit from the
> forked task. Perhaps we should just clear the bit in the function.

If that were to fix this test case, I think it would be incidental rather
than meaning the right thing.  The "this task wants single-stepping" state
should not have anything to do with TIF_SINGLE_STEP.  It means "this task
recently had single-stepping", which is a separate moving part.

Thanks,
Roland
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