linux-kernel - Re: [RFC PATCH v1.9 05/14] sched: horrible way to detect whether a task has been preempted

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Message-ID: <20160408080710.GF5218@pathway.suse.cz>
Date:	Fri, 8 Apr 2016 10:07:10 +0200
From:	Petr Mladek <pmladek@...e.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Jiri Kosina <jikos@...nel.org>, Jessica Yu <jeyu@...hat.com>,
	Miroslav Benes <mbenes@...e.cz>, linux-kernel@...r.kernel.org,
	live-patching@...r.kernel.org, Vojtech Pavlik <vojtech@...e.com>
Subject: Re: [RFC PATCH v1.9 05/14] sched: horrible way to detect whether a
 task has been preempted

On Thu 2016-04-07 09:34:03, Josh Poimboeuf wrote:
> On Thu, Apr 07, 2016 at 11:47:00AM +0200, Petr Mladek wrote:
> > On Wed 2016-04-06 11:33:56, Josh Poimboeuf wrote:
> > > On Wed, Apr 06, 2016 at 03:06:19PM +0200, Petr Mladek wrote:
> > We could even move this check into the livepatch code but then
> > print_context_stack_reliable() will not always give reliable results.
> 
> Why would moving the check to the livepatch code affect the reliability
> of print_context_stack_reliable()?

print_context_stack_reliable() is a generic function that might
eventualy be used also outside livepatch code. If there is
preempt_schedule_irq() on the stack, it means that the rest
of the stack might be unreliable and it should be detected
by the function itself.

Let's forget the idea of moving the check into the livepatch
code :-)

Best Regards,
Petr