> From: Kimberly Brown <kimbrownkd@xxxxxxxxx> > Sent: Thursday, January 31, 2019 9:47 AM > ... > 2) Prevent a deadlock that can occur between the proposed mutex_lock() > call in the vmbus_chan_attr_show() function and the sysfs/kernfs functions. Hi Kim, Can you please share more details about the deadlock? It's unclear to me how the deadlock happens. > I've identified two possible solutions to the deadlock: > > 1) Add a new mutex to the vmbus_channel struct which protects changes to > "channel->state". Use this new mutex in vmbus_chan_attr_show() instead of > "vmbus_connection.channel_mutex". > > 2) Use "vmbus_connection.channel_mutex" in vmbus_chan_attr_show() as > originally proposed, and acquire it with mutex_trylock(). If the mutex > cannot be acquired, return -EINVAL. It looks more like a workaround. IMO we should try to find a real fix. :-) > I'm leaning towards (2), using mutex_trylock(). > "vmbus_connection.channel_mutex" > appears to be used only when a channel is being opened or closed, so > vmbus_chan_attr_show() should be able to acquire the mutex when the > channel is in use. > > If anyone has suggestions, please let me know. > > Thanks, > Kim Thanks, -- Dexuan _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
