linux-kernel - Re: [PATCH] watchdog: mena21_wdt: Fix a possible data race in a21_wdt_set

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Date:   Tue, 8 May 2018 11:47:37 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>, morbidrsa@...il.com,
        wim@...ux-watchdog.org
Cc:     linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: mena21_wdt: Fix a possible data race in
 a21_wdt_set_timeout



On 2018/5/8 11:42, Guenter Roeck wrote:
> On 05/07/2018 08:32 PM, Jia-Ju Bai wrote:
>>
>>
>> On 2018/5/8 11:28, Guenter Roeck wrote:
>>> On 05/07/2018 08:18 PM, Jia-Ju Bai wrote:
>>>> The write operation to "wdt->timeout" is protected by
>>>> the lock on line 118, but the read operation to
>>>> this data on line 105 is not protected by the lock.
>>>> Thus, there may exist a data race for "wdt->timeout".
>>>>
>>>> To fix this data race, the read operation to "wdt->timeout"
>>>> should be also protected by the lock.
>>>>
>>>
>>> There is no race. There is already a mutex in the watchdog core 
>>> which serializes
>>> calls to the various API functions. It would make more sense to drop 
>>> drv->lock
>>> from the driver.
>>>
>>
>> Thanks for your reply :)
>> Need I submit a patch of dropping all calls to "drv->lock"?
>>
>
> You don't _need_ to, but I would happily give it my Reviewed-by: tag 
> if you do.
>

Okay, I will write a patch today :)


Best wishes,
Jia-Ju Bai