From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leo Yan Subject: Re: [PATCH V2 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver Date: Tue, 27 Mar 2018 11:43:44 +0800 Message-ID: <20180327034344.GC21693@leoy-ThinkPad-X240s> References: <1519226968-19821-1-git-send-email-daniel.lezcano@linaro.org> <1519226968-19821-7-git-send-email-daniel.lezcano@linaro.org> <20180223073432.GF26947@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Daniel Lezcano Cc: Viresh Kumar , edubezval@gmail.com, kevin.wangtao@linaro.org, vincent.guittot@linaro.org, amit.kachhap@gmail.com, linux-kernel@vger.kernel.org, javi.merino@kernel.org, rui.zhang@intel.com, daniel.thompson@linaro.org, linux-pm@vger.kernel.org List-Id: linux-pm@vger.kernel.org On Fri, Feb 23, 2018 at 12:28:51PM +0100, Daniel Lezcano wrote: > On 23/02/2018 08:34, Viresh Kumar wrote: > > On 21-02-18, 16:29, Daniel Lezcano wrote: > [ ... ] > > >> +static s64 cpuidle_cooling_runtime(struct cpuidle_cooling_device *idle_cdev) > >> +{ > >> + s64 next_wakeup; > >> + int state = idle_cdev->state; > >> + > >> + /* > >> + * The function must never be called when there is no > >> + * mitigation because: > >> + * - that does not make sense > >> + * - we end up with a division by zero > >> + */ > >> + BUG_ON(!state); > > > > As there is no locking in place, we can surely hit this case. What if > > the state changed to 0 right before this routine was called ? > > > > I would suggest we should just return 0 in that case and get away with > > the BUG_ON(). Here if 'state' equals to 0 and we return 0, then the return value will be same with when 'state' = 100; this lets the return value confused. I think for 'state' = 0, should we return -1 so indicate the hrtimer will not be set for this case? Thanks, Leo Yan