Commits
Bill Kuzeja committed 8de66b0e6a5
xhci: Prevent deadlock when xhci adapter breaks during init
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: <stable@vger.kernel.org> # v4.17+
Cc: Torez Smith <torez@redhat.com>
Signed-off-by: Bill Kuzeja <william.kuzeja@stratus.com>
Signed-off-by: Torez Smith <torez@redhat.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/1570190373-30684-7-git-send-email-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>