[Bug 220272] New: 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

            Bug ID: 220272
           Summary: Latent race condition in USB code unveiled with
                    optimized memset_64.S
           Product: Drivers
           Version: 2.5
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: USB
          Assignee: drivers_usb@kernel-bugs.kernel.org
          Reporter: m.seyfarth@gmail.com
        Regression: No

Created attachment 308313
  --> https://bugzilla.kernel.org/attachment.cgi?id=308313&action=edit
Optimized memset_64.S for Intel Raptor Lake

Experimenting with AI to tune memset_64.S (see the attached file) for my Intel
14700KF-system unveiled a race condition in the USB code.

Once this significantly faster memset implementation is compiled-in, I've
noticed that my USB mouse (Sharkoon Light2 100) is not recognized/detected any
longer after each re-boot. The USB mouse is placed in one of the top USB slot
next to my USB keyboard (which surprisingly still works fine) on my NZXT N5
Z690 motherboard. Which one doesn't matter.

I did not get any suspect dmesg entries, the mouse is simply not recognized at
all.

I first thought of a hardware issue or defective USB slot, but re-slotting the
mouse in a different USB slot did not fix the problem eventually. The mouse
initially works fine there until the next reboot.

It also starts to work fine in the same USB slot where it wasn't recognized
after a reboot once I unplug it and plug it in the same USB slot again.

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