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Date: Wed, 06 Jan 2021 09:20:44 +0800 From: Can Guo <cang@...eaurora.org> To: Bean Huo <huobean@...il.com> Cc: asutoshd@...eaurora.org, nguyenb@...eaurora.org, hongwus@...eaurora.org, ziqichen@...eaurora.org, rnayak@...eaurora.org, linux-scsi@...r.kernel.org, kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com, rjw@...ysocki.net, Alim Akhtar <alim.akhtar@...sung.com>, Avri Altman <avri.altman@....com>, "James E.J. Bottomley" <jejb@...ux.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, Stanley Chu <stanley.chu@...iatek.com>, Bean Huo <beanhuo@...ron.com>, Nitin Rawat <nitirawa@...eaurora.org>, Adrian Hunter <adrian.hunter@...el.com>, Bart Van Assche <bvanassche@....org>, Satya Tangirala <satyat@...gle.com>, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 2/2] scsi: ufs: Protect PM ops and err_handler from user access through sysfs Hi Bean, On 2021-01-06 02:38, Bean Huo wrote: > On Tue, 2021-01-05 at 09:07 +0800, Can Guo wrote: >> On 2021-01-05 04:05, Bean Huo wrote: >> > On Sat, 2021-01-02 at 05:59 -0800, Can Guo wrote: >> > > + * @shutting_down: flag to check if shutdown has been invoked >> > >> > I am not much sure if this flag is need, since once PM going in >> > shutdown path, what will be returnded by pm_runtime_get_sync()? >> > >> > If pm_runtime_get_sync() will fail, just check its return. >> > >> >> That depends. During/after shutdown, for UFS's case only, >> pm_runtime_get_sync(hba->dev) will most likely return 0, >> because it is already RUNTIME_ACTIVE, pm_runtime_get_sync() >> will directly return 0... meaning you cannot count on it. >> >> Check Stanley's change - >> https://lore.kernel.org/patchwork/patch/1341389/ >> >> Can Guo. > > Can, > > Thanks for pointing out that. > > Based on my understanding, that patch is redundent. maybe I > misundestood Linux shutdown sequence. Sorry, do you mean Stanley's change is redundant? > > I checked the shutdown flow: > > 1. Set the "system_state" variable > 2. Disable usermod to ensure that no user from userspace can start a > request I hope it is like what you interpreted, but step #2 only stops UMH(#265) but not all user space activities. Whereas, UMH is for kernel space calling user space. 264 system_state = state; 265 usermodehelper_disable(); 266 device_shutdown(); Thanks, Can Guo. > 3. device_shutdown() > So, userspace thread can not start a request to trigger runtime > resume(pm_runtime_get_sync) after step 2. > > also, no need to add that flag to checkup if shutdwon is running, > maybe it is better to check variable system_state: > > if (system_state == SYSTEM_POWER_OFF || system_state == SYSTEM_HALT > || system_state == SYSTEM_RESTART) > //shutdown start > > > I still hope Rafael or someone else can confirm that if > pm_runtime_get_sync() will really return ok in shutdown flow. > > > thanks, > Bean > >> >> > Hi Rafael >> > would you please help us confirm this? >> > >> > thanks, >> > Bean
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