From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Subject: Re: Re: [PATCH] media: staging: tegra-vde: fix runtime pm imbalance on error Date: Thu, 28 May 2020 15:08:18 +0300 Message-ID: <20200528120818.GO22511@kadam> References: <20200520095148.10995-1-dinghao.liu@zju.edu.cn> <2b5d64f5-825f-c081-5d03-02655c2d9491@gmail.com> <20200520150230.GC30374@kadam> <2a46539d.b977f.1723553aa81.Coremail.dinghao.liu@zju.edu.cn> <20200521091505.GF30374@kadam> <20200521173901.GA22310@kadam> <20200522131031.GL2163848@ulmo> <20200522132318.GM30374@kadam> <20200522144312.GA2374603@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200522144312.GA2374603@ulmo> Sender: linux-kernel-owner@vger.kernel.org To: Thierry Reding Cc: devel@driverdev.osuosl.org, Len Brown , Pavel Machek , "Rafael J. Wysocki" , Greg Kroah-Hartman , Linux PM , "Rafael J. Wysocki" , Linux Kernel Mailing List , Jonathan Hunter , linux-tegra , dinghao.liu@zju.edu.cn, Kangjie Lu , Dmitry Osipenko , Mauro Carvalho Chehab , linux-media@vger.kernel.org List-Id: linux-tegra@vger.kernel.org On Fri, May 22, 2020 at 04:43:12PM +0200, Thierry Reding wrote: > On Fri, May 22, 2020 at 04:23:18PM +0300, Dan Carpenter wrote: > > On Fri, May 22, 2020 at 03:10:31PM +0200, Thierry Reding wrote: > > > On Thu, May 21, 2020 at 08:39:02PM +0300, Dan Carpenter wrote: > > > > On Thu, May 21, 2020 at 05:22:05PM +0200, Rafael J. Wysocki wrote: > > > > > On Thu, May 21, 2020 at 11:15 AM Dan Carpenter wrote: > > > > > > > > > > > > On Thu, May 21, 2020 at 11:42:55AM +0800, dinghao.liu@zju.edu.cn wrote: > > > > > > > Hi, Dan, > > > > > > > > > > > > > > I agree the best solution is to fix __pm_runtime_resume(). But there are also > > > > > > > many cases that assume pm_runtime_get_sync() will change PM usage > > > > > > > counter on error. According to my static analysis results, the number of these > > > > > > > "right" cases are larger. Adjusting __pm_runtime_resume() directly will introduce > > > > > > > more new bugs. Therefore I think we should resolve the "bug" cases individually. > > > > > > > > > > > > > > > > > > > That's why I was saying that we may need to introduce a new replacement > > > > > > function for pm_runtime_get_sync() that works as expected. > > > > > > > > > > > > There is no reason why we have to live with the old behavior. > > > > > > > > > > What exactly do you mean by "the old behavior"? > > > > > > > > I'm suggesting we leave pm_runtime_get_sync() alone but we add a new > > > > function which called pm_runtime_get_sync_resume() which does something > > > > like this: > > > > > > > > static inline int pm_runtime_get_sync_resume(struct device *dev) > > > > { > > > > int ret; > > > > > > > > ret = __pm_runtime_resume(dev, RPM_GET_PUT); > > > > if (ret < 0) { > > > > pm_runtime_put(dev); > > > > return ret; > > > > } > > > > return 0; > > > > } > > > > > > > > I'm not sure if pm_runtime_put() is the correct thing to do? The other > > > > thing is that this always returns zero on success. I don't know that > > > > drivers ever care to differentiate between one and zero returns. > > > > > > > > Then if any of the caller expect that behavior we update them to use the > > > > new function. > > > > > > Does that really have many benefits, though? I understand that this > > > would perhaps be easier to use because it is more in line with how other > > > functions operate. On the other hand, in some cases you may want to call > > > a different version of pm_runtime_put() on failure, as discussed in > > > other threads. > > > > I wasn't CC'd on the other threads so I don't know. :/ > > It was actually earlier in this thread, see here for example: > > http://patchwork.ozlabs.org/project/linux-tegra/patch/20200520095148.10995-1-dinghao.liu@zju.edu.cn/#2438776 I'm not seeing what you're talking about. The only thing I see in this thread is that we don't want to call pm_runtime_mark_last_busy(dev) which updates the last_busy time that is used for autosuspend. The other thing that was discussed was pm_runtime_put_noidle() vs pm_runtime_put_autosuspend(). "The pm_runtime_put_noidle() should have the same effect as yours variant". So apparently they are equivalent in this situation. How should we choose one vs the other? I'm not trying to be obtuse. I understand that probably if I worked in PM then I wouldn't need documentation... :/ regards, dan carpenter