linux-kernel - Re: [RFC PATCH 6/9] livepatch: create per-task consistency model

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Message-ID: <54DCAA12.9070400@suse.cz>
Date:	Thu, 12 Feb 2015 14:26:42 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>, Vojtech Pavlik <vojtech@...e.cz>
Subject: Re: [RFC PATCH 6/9] livepatch: create per-task consistency model

On 02/12/2015, 04:21 AM, Josh Poimboeuf wrote:
> Ingo, Peter,
> 
> Would you have any objections to making task_rq_lock/unlock() non-static
> (or moving them to kernel/sched/sched.h) so they can be called by the
> livepatch code?
> 
> To provide some background, I'm looking for a way to temporarily prevent
> a sleeping task from running while its stack is examined, to decide
> whether it can be safely switched to the new patching "universe".  For
> more details see klp_transition_task() in the patch below.
> 
> Using task_rq_lock() is the most straightforward way I could find to
> achieve that.

Hi, I cannot speak whether it is the proper way or not.

But if so, would it make sense to do the opposite: expose an API to walk
through the processes' stack and make the decision? Concretely, move
parts of klp_stacktrace_address_verify_func to sched.c or somewhere in
kernel/sched/ and leave task_rq_lock untouched.

regards,
-- 
js
suse labs
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