[Nouveau] [Bug 100567] Nouveau system freeze fifo: SCHED_ERROR 0a [CTXSW_TIMEOUT]

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=100567

--- Comment #28 from Roy <nouveau at spliet.org> ---
Somewhat surprised that this particular report hasn't received any attention
from a core dev. Sadly, I'm afraid my response will not be hugely satisfying
eiter.

The message "fifo: SCHED_ERROR 0a [CTXSW_TIMEOUT]" is not the result of *a bug*
and does not point in the direction of one. Rather it is a symptom of a wide
variety of potential problems with nouveau, (all of) which result in a hang of
the rendering part of the GPU. On itself it doesn't give meaningful information
to any developer as to what may be the culprit. It's like measuring a fever, it
could be the result of many conditions.

Developers would be helped if there was a reliably reproducible situation in
which this event can be triggered. If there is a list of steps that can be
followed that would result in this message and a hang, that somehow doesn't
involve words like "random" or "wait for possibly a few hours", and that can be
traced with tools such as APITrace, we could get a step further in analysing
what goes wrong. However, it seems unlikely this is the case, especially since
we are also aware of multithreading-related issues that make isolating such
problems extremely difficult. Unfortunately, post-mortem syslogs and dmesgs are
unlikely to add any useful information to this or similar bug reports.

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