linux-kernel - Re: [RFC PATCH v1.9 00/14] livepatch: hybrid consistency model

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Date:	Fri, 1 Apr 2016 15:34:47 +0200 (CEST)
From:	Miroslav Benes <mbenes@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
cc:	Jiri Kosina <jikos@...nel.org>, Jessica Yu <jeyu@...hat.com>,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Vojtech Pavlik <vojtech@...e.com>
Subject: Re: [RFC PATCH v1.9 00/14] livepatch: hybrid consistency model

> - actually test it

I did slightly and it partially worked and partially it did not.

When I applied sample livepatch module, /proc/cmdline was patched and when 
I called 'cat /proc/cmdline' I got the correct livepatched message. So far 
so good. But the patching itself never finished because of many processes 
with unreliable stacks. It almost looked like every sleeping process was 
reported. I haven't debugged that yet.

Second, I have a simple test case. Kthread which sleeps in to-be-patched 
function foo() for a while and then it sleeps somewhere else and that in a 
loop. After live patch application the kthread is reported to have 
unreliable stack and it is not migrated. The good thing is that also the 
function foo() from the old universe is called and thus the consistency 
model works.

So I guess there is some problem in a stack checking...

Miroslav