[Bug 100258] [BAT][SKL] Serial console hung in kms_flip when running IGT

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=100258

--- Comment #1 from Chris Wilson <chris at chris-wilson.co.uk> ---
Each character has a 1s timeout in wait_for_xmitr. If the string was log enough
and the serial console bust, it can easily appear to be hung. As wait_for_xmitr
keeps poking the nmi watchdog. the slow loop will not be caught. If that is
correct, this appears to be a hw issue.

An alternative hypothesis is that the usb device struct sent garbage to be
printed and it really is stuck printing out all of memory, 1 character at a
time. Kasan might help.

I don't think the vtcon switch of modes is significant.

What would be useful is the dmesg before to see if we can identify what usb
event triggered.

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