linux-kernel - Re: [PATCH 2/2] scsi: ufs: Protect PM ops and err

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Date:   Tue, 05 Jan 2021 09:07:24 +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

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.

> Hi Rafael
> would you please help us confirm this?
> 
> thanks,
> Bean
> 
> 
>> + * @host_sem: semaphore used to serialize concurrent contexts
>>   * @eh_wq: Workqueue that eh_work works on
>>   * @eh_work: Worker to handle UFS errors that require s/w attention
>>   * @eeh_work: Worker to handle exception events
>> @@ -751,7 +753,8 @@ struct ufs_hba {
>>         u32 intr_mask;
>>         u16 ee_ctrl_mask;
>>         bool is_powered;
>> -       struct semaphore eh_sem;
>> +       bool shutting_down;
>> +       struct semaphore host_sem;