Hello again, Lai. On Fri, Sep 07, 2012 at 12:29:39PM -0700, Tejun Heo wrote: > > Since we introduce manage_mutex(), any palace should be allowed to grab it > > when its context allows. So it is not hotplug code's responsibility of this > > bug. > > > > manage_workers() just use mutex_trylock() to grab the lock, it does not make > > hard to do it jobs when need, and it does not try to find out the reason of > > fail. > > so I think it is manage_workers()'s responsibility to handle this bug. > > a manage_workers_slowpath() is enough to fix the bug. > > It doesn't really matter how the synchronization between regular > manager and hotplug path is done. The point is that hotplug path, as > much as possible, should be responsible for any incurred complexities, > so I'd really like to stay away from adding a completely different > path manager can be invoked in the usual path if at all possible. > Let's try to solve this from the hotplug side.
So, how about something like the following? * Make manage_workers() called outside gcwq->lock (or drop gcwq->lock after checking MANAGING). worker_thread() can jump back to woke_up: instead. * Distinguish synchronization among workers and against hotplug. Was this what you tried with non_manager_mutex? Anyways, revive WORKER_MANAGING to synchronize among workers. If the worker won MANAGING, drop gcwq->lock and mutex_lock() gcwq->hotplug_mutex and then do other stuff. This should prevent any idle worker passing through manage_workers() while hotplug is in progress. Do you think it would work? Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
