[Bug 220272] Latent race condition in USB code unveiled with optimized memset_64.S

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=220272

--- Comment #19 from Alan Stern (stern@rowland.harvard.edu) ---
It's great that the mouse remains non-working after Michał's test!

You should collect two usbmon traces for bus 1.  For the first, start the trace
before issuing the second test command and don't end the trace until after you
have tried (and failed!) to use the mouse.  Example:

echo 0000:00:14.0 > /sys/bus/pci/drivers/xhci_hcd/unbind
cat /sys/kernel/debug/usb/usbmon/1u >usbmon1.dat &
echo 0000:00:14.0 > /sys/bus/pci/drivers/xhci_hcd/bind
(try to move the mouse)
fg
^C

For the second, unplug the mouse, then start the trace, then plug the mouse
back in.  Don't end the trace until after you have tried (and succeeded!) to
use the mouse.

The traces will be easier to read if you disconnect as many of the other USB
devices on your system as possible.

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