On 3/9/21 5:03 PM, Tetsuo Handa wrote:
On 2021/03/10 8:52, Shuah Khan wrote:
On 3/9/21 4:40 PM, Tetsuo Handa wrote:
On 2021/03/10 4:50, Shuah Khan wrote:
On 3/9/21 4:04 AM, Tetsuo Handa wrote:
On 2021/03/09 1:27, Shuah Khan wrote:
Yes. We might need synchronization between events, threads, and shutdown
in usbip_host side and in connection polling and threads in vhci.
I am also looking at the shutdown sequences closely as well since the
local state is referenced without usbip_device lock in these paths.
I am approaching these problems as peeling the onion an expression so
we can limit the changes and take a spot fix approach. We have the
goal to address these crashes and not introduce regressions.
I think my [PATCH v4 01/12]-[PATCH v4 06/12] simplify your further changes
without introducing regressions. While ud->lock is held when checking ud->status,
current attach/detach code is racy about read/update of ud->status . I think we
can close race in attach/detach code via a simple usbip_event_mutex serialization.
Do you mean patches 1,2,3,3,4,5,6?
Yes, my 1,2,3,4,5,6.
Since you think that usbip_prepare_threads() does not worth introducing, I'm fine with
replacing my 7,8,9,10,11,12 with your "[PATCH 0/6] usbip fixes to crashes found by syzbot".
Using event lock isn't the right approach to solve the race. It is a
large grain lock. I am not looking to replace patches.
It is not a large grain lock. Since event_handler() is exclusively executed, this lock
does _NOT_ block event_handler() unless attach/detach operations run concurrently.
event handler queues the events. It shouldn't be blocked by attach
and detach. The events could originate for various reasons during
the host and vhci operations. I don't like using this lock for
attach and detach.
I still haven't seen any response from you about if you were able to
verify the fixes I sent in fix the problem you are seeing.
> I won't be able to verify your fixes, for it is syzbot who is seeing
the problem.
Thank you for letting me know.
thanks,
-- Shuah
