Re: [PATCH 1/3] driver core: Fix concurrent problem of deferred_probe_extend_timeout()

["wangwensheng (C)" <wangwensheng4@huawei.com>]

在 2025/8/14 19:37, Greg KH 写道:
> On Thu, Aug 14, 2025 at 07:10:21PM +0800, Wang Wensheng wrote:
>> The deferred_probe_timeout_work may be canceled forever unexpected when
>> deferred_probe_extend_timeout() executes concurrently. Start with
>> deferred_probe_timeout_work pending, and the problem would
>> occur after the following sequence.
>>
>>           CPU0                                 CPU1
>> deferred_probe_extend_timeout
>>    -> cancel_delayed_work => true
>>                                       deferred_probe_extend_timeout
>>                                         -> cancel_delayed_wrok
>>                                           -> __cancel_work
>>                                             -> try_grab_pending
>>    -> schedule_delayed_work
>>     -> queue_delayed_work_on
>> since pending bit is grabbed,
>> just return without doing anything
>>                                          -> set_work_pool_and_clear_pending
>>                                       this __cancel_work return false and
>>                                       the work would never be queued again
>>
>> The root cause is that the PENDING_BIT of the work_struct would be set
>> temporaily in __cancel_work and this bit could prevent the work_struct
>> to be queued in another CPU.
>>
>> Use deferred_probe_mutex to protect the cancel and queue operations for
>> the deferred_probe_timeout_work to fix this problem.
>>
>> Fixes: 2b28a1a84a0e ("driver core: Extend deferred probe timeout on driver registration")
>> Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>
>> ---
>>   drivers/base/dd.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
>> index 13ab98e033ea..1983919917e0 100644
>> --- a/drivers/base/dd.c
>> +++ b/drivers/base/dd.c
>> @@ -323,6 +323,7 @@ static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_
>>   
>>   void deferred_probe_extend_timeout(void)
>>   {
>> +	mutex_lock(&deferred_probe_mutex);
> 
> Perhaps use a guard() instead?
> 
> thanks,
> 
> greg k-h
> 

Thanks for your suggestion. I have sent a v2 for this signle patch, 
because the other issue is not strongly related to this and need
more discussion.