[Intel-gfx] [PATCH v2] drm/i915/execlists: Listen to COMPLETE context event not ACTIVE_IDLE

[Chris Wilson]

Quoting Chris Wilson (2017-11-18 01:05:24)
> Since commit e1fee72c2ea2e9c0c6e6743d32a6832f21337d6c
> Author: Oscar Mateo <oscar.mateo at intel.com>
> Date:   Thu Jul 24 17:04:40 2014 +0100
> 
>     drm/i915/bdw: Avoid non-lite-restore preemptions
> 
> execlists has listened to (ACTIVE_IDLE | ELEMENT_SWITCH) for detecting
> when one context completed and it either continued onto the next (in port
> 1) or idled. We would always see COMPLETE | ACTIVE_IDLE on the final
> context-switch event, but on recent gen it appears that we now get
> separate ACTIVE_IDLE and COMPLETE events. In particular, the ACTIVE_IDLE
> events may not be coupled to a context (since it is a general state rather
> than a specific context completion event).
> 
> v2: Update the history, execlists did originally start out by listening
> to the COMPLETE event not ACTIVE_IDLE.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=103800

> References: https://bugs.freedesktop.org/show_bug.cgi?id=102035
Scrap that, the difference was kasan masking the race.
-Chris