[Bug 221184] mouse/keyboard (connected via hub) usb reset under system load with weak cpu

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221184

--- Comment #35 from Alan Stern (stern@rowland.harvard.edu) ---
Yes, EPROTO represents a communication failure.  However, it only means that
the host thinks there was a failure; there's no way to know what the device
thinks.  Furthermore, xHCI controllers require an endpoint reset in order to
recover from the failure.

As a result of these two facts, it is entirely possible that the endpoint state
held in the host is no longer in agreement with the state held in the device. 
If it isn't, a retry would apparently succeed but in fact the device would
ignore the data that was sent or repeat the data that it sent previously, or
maybe not respond at all.

The only way to make sure the two states are back in agreement is to reset them
both.  That's what usb_clear_halt() does.

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