On 23.9.2019 16.58, Bill Kuzeja wrote:
The system can hit a deadlock if an xhci adapter breaks while initializing.
The deadlock is between two threads: thread 1 is tearing down the
adapter and is stuck in usb_unlocked_disable_lpm waiting to lock the
hcd->handwidth_mutex. Thread 2 is holding this mutex (while still trying
to add a usb device), but is stuck in xhci_endpoint_reset waiting for a
stop or config command to complete. A reboot is required to resolve.
It turns out when calling xhci_queue_stop_endpoint and
xhci_queue_configure_endpoint in xhci_endpoint_reset, the return code is
not checked for errors. If the timing is right and the adapter dies just
before either of these commands get issued, we hang indefinitely waiting
for a completion on a command that didn't get issued.
This wasn't a problem before the following fix because we didn't send
commands in xhci_endpoint_reset:
commit f5249461b504 ("xhci: Clear the host side toggle manually when
endpoint is soft reset")
With the patch I am submitting, a duration test which breaks adapters
during initialization (and which deadlocks with the standard kernel) runs
without issue.
Fixes: f5249461b504 ("xhci: Clear the host side toggle manually when
endpoint is soft reset")
Cc: Mathias Nyman <mathias.nyman@xxxxxxxxx>
Cc: Torez Smith <torez@xxxxxxxxxx>
Signed-off-by: Bill Kuzeja <william.kuzeja@xxxxxxxxxxx>
Signed-off-by: Torez Smith <torez@xxxxxxxxxx>
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Thanks, adding to queue
-Mathias
