linux-kernel - Re: [PATCH v3 22/22] thermal/intel_powerclamp: Convert the kthread to kthread worker API

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Date:	Mon, 11 Jan 2016 18:17:18 -0800
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	linux-pm@...r.kernel.org, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v3 22/22] thermal/intel_powerclamp: Convert the kthread
 to kthread worker API

On Fri, 8 Jan 2016 17:49:31 +0100
Petr Mladek <pmladek@...e.com> wrote:

> Is the __preempt_schedule() a problem? It allows to switch the process
> when needed. I thought that it was safe because try_to_freeze() might
> have slept as well.
> 
not a problem. i originally thought queue_kthread_work() may add
delay but it doesn't since there is no other work on this kthread.
> 
> > - vulnerable to future changes of queuing work  
> 
> The question is if it is safe to sleep, freeze, or even migrate
> the system between the works. It looks like because of the
> try_to_freeze() and schedule_interrupt() calls in the original code.
> 
> BTW: I wonder if the original code correctly handle freezing after
> the schedule_timeout(). It does not call try_to_freeze()
> there and the forced idle states might block freezing.
> I think that the small overhead of kthread works is worth
> solving such bugs. It makes it easier to maintain these
> sleeping states.
it is in a while loop, so try_to_freeze() gets called. Am I missing
something?

Thanks,

Jacob