Alan Stern wrote:
The current code does use down_*_trylock, and it does check the device state for disconnect-in-progress. If things don't work out, it sleeps for a short while and then tries again.
I think the error handler should rather give SUCCESS back to scsi if it knows the device was or is being disconnected. After that, commands would be enqueued again, and these commands would be immediately done() with an appropriate result code. IMO the error handler should return SUCCESS rather than FAILED because, if the device is diconnected, there is simply nothing left to do that could advance recovery from error. Retries (in the error handler) will not help with error recovery either. Or do you retry in hope that the device might be reconnected and then a device reset should happen? A more general thought: It appears from the example you explained that maybe the USB highlevel carries too much of a burden to watch out for concurrency. Tasks like to mutually exclude port resets and disconnects --- which seems to me to be a task unspecific to highlevel protocols, correct me if I'm wrong --- might be better moved into the USB core. Then the highlevel would have to worry less about how exactly to avoid races and deadlocks, only about _what_ to do if there is a conflict. (The kind of conflict should be indicated by the core by means of return values or status flags or the like.) But I am of course speaking without any knowledge about USB and Linux' USB stack. -- Stefan Richter -=====-=-=-= =--- -=--= http://arcgraph.de/sr/ - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
