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Date:   Fri, 18 Dec 2020 13:42:35 +0800
From:   Can Guo <cang@codeaurora.org>
To:     Bean Huo <huobean@gmail.com>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        hongwus@codeaurora.org, rnayak@codeaurora.org,
        linux-scsi@vger.kernel.org, kernel-team@android.com,
        saravanak@google.com, salyzyn@google.com,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Bean Huo <beanhuo@micron.com>,
        Bart Van Assche <bvanassche@acm.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2 1/1] scsi: ufs: Fix a possible NULL pointer issue
In-Reply-To: <7eb8f335f4eb85385f54c88952f7749750340320.camel@gmail.com>
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 <7eb8f335f4eb85385f54c88952f7749750340320.camel@gmail.com>
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On 2020-12-14 22:32, Bean Huo wrote:
> On Sun, 2020-12-13 at 19:41 -0800, Can Guo wrote:
>> Fixes: 88a92d6ae4fe ("scsi: ufs: Serialize eh_work with system PM
>> events and async scan")
>> 
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index c1c401b..ef155a9 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -8883,8 +8883,11 @@ int ufshcd_system_suspend(struct ufs_hba *hba)
>>         int ret = 0;
>>         ktime_t start = ktime_get();
>> 
>> +       if (!hba)
>> +               return 0;
>> +
>>         down(&hba->eh_sem);
>> -       if (!hba || !hba->is_powered)
>> +       if (!hba->is_powered)
>>                 return 0;
> 
> 
> Can,
> 
> why not moving down(&hba->eh_sem) after "return 0;"?

In your way, if hba is not powered, ufshcd_system_suspend() returns
0, which is a successful suspend. When ufshcd_system_resume() is called,
if hba is not powered, it goes to out and does up(&hba->eh_sem), which
shall cause unbalance to eh_sem.

Thanks,

Can Guo.