From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacob Pan Subject: Re: [PATCH v3 22/22] thermal/intel_powerclamp: Convert the kthread to kthread worker API Date: Tue, 12 Jan 2016 08:20:21 -0800 Message-ID: <20160112082021.6a28dc66@icelake> References: <1447853127-3461-1-git-send-email-pmladek@suse.com> <1447853127-3461-23-git-send-email-pmladek@suse.com> <20160107115531.34279a9b@icelake> <20160108164931.GT3178@pathway.suse.cz> <20160111181718.0ace4a58@yairi> <20160112101129.GN731@pathway.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com ([192.55.52.88]:16360 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752671AbcALQVe (ORCPT ); Tue, 12 Jan 2016 11:21:34 -0500 In-Reply-To: <20160112101129.GN731@pathway.suse.cz> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Petr Mladek Cc: Andrew Morton , Oleg Nesterov , Tejun Heo , Ingo Molnar , Peter Zijlstra , Steven Rostedt , "Paul E. McKenney" , Josh Triplett , Thomas Gleixner , Linus Torvalds , Jiri Kosina , Borislav Petkov , Michal Hocko , linux-mm@kvack.org, Vlastimil Babka , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Zhang Rui , Eduardo Valentin , linux-pm@vger.kernel.org, jacob.jun.pan@linux.intel.com On Tue, 12 Jan 2016 11:11:29 +0100 Petr Mladek wrote: > > > 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? > > But it might take some time until try_to_freeze() is called. > If I get it correctly. try_to_freeze_tasks() wakes freezable > tasks to get them into the fridge. If clamp_thread() is waken > from that schedule_timeout_interruptible(), it still might inject > the idle state before calling try_to_freeze(). It means that freezer > needs to wait "quite" some time until the kthread ends up in the > fridge. > > Hmm, even my conversion does not solve this entirely. We might > need to call freezing(current) in the > > while (time_before(jiffies, target_jiffies)) { > > cycle. And break injecting the idle state when freezing is requested. The injection time for each period is very short, default 6ms. While on the other side the default freeze timeout is 20 sec. So I think task freeze can wait :) i.e. unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;