linux-kernel - Re: s390 && user_enable_single_step() (Was: odd utrace testing results on s390x)

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Date:	Thu,  7 Jan 2010 13:44:29 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Martin Schwidefsky <schwidefsky@...ibm.com>, caiqian@...hat.com,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Jan Kratochvil <jkratoch@...hat.com>,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	utrace-devel@...hat.com
Subject: Re: s390 && user_enable_single_step() (Was: odd utrace testing
	results on s390x)

> Can't understand why do we need TIF_SINGLE_STEP at all.

I think you mean "why we need to set it in do_signal" here,
not "why do we need it to exist at all".

> Just pass current->thread.per_info.single_step to
> tracehook_signal_handler() ?

Yes.  I believe this is what Martin meant, and it's what I meant to endorse.

do_signal should not do anything with TIF_SINGLE_STEP at all.
Its only purpose should be to communicate from the low-level
trap assembly code up to the return-to-user assembly code so
it calls do_single_step.

Thanks,
Roland
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