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> > > + struct hlist_node *tmp; > > > + > > > + mutex_lock(&pf->mac_list_lock); > > > > The mutex_lock() usage here should raise serious questions. This is > > running right before mutex_destroy(). So if there were any concurrent > > attempt to acquire this lock, that concurrent code would have been broken > > any time it would have lost arbitration, by the fact that it would > > attempt to acquire a destroyed mutex. > > > > But there's no such concurrent thread, because we run after destroy_workqueue() > > which flushes those concurrent calls and prevents new ones. So the mutex > > usage here is not necessary. > > > > [ same thing with mutex_init() immediately followed by mutex_lock(). > > It is an incorrect pattern most of the time. ] > > > > This is not as bad as it seems. In the final version of the code, mutex 'mac_list_lock' > serializes the access btw the thread programming the filter for the PF instance, > and the threads programming the filter on behalf of underlying VFs (triggered by async > request from VF). But since VF support is not included in this patch set (as Wei > already mentioned) the lock can/should be added later, with the VF patches. We all agree that the lock is unnecessary as far as the logic presented in this patch set is concerned, and thus should not be added. When Wei will present new code that will make explicit serialization necessary, we can comment more. But, I don't see how any extra logic can change the basic fact I was pointing out in the portion that you've quoted. Before you destroy the mutex, you need to do something that ensures concurrent threads can no longer execute. Then, there's no point in locking in enetc4_pf_destroy_mac_list(). I expect not to see such locking there in future patch sets.