[Intel-gfx] [PATCH] drm/i915: Put all non-blocking modesets onto an ordered wq

[Maarten Lankhorst]

Op 13-11-17 om 14:36 schreef Ville Syrjala:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> We have plenty of global registers and whatnot programmed without
> any further locking by the modeset code. Currently non-bocking
> modesets are allowed to execute in parallel which could corrupt
> said registers.
>
> To avoid the problem let's run all non-blocking modesets on an
> ordered workqueue. We still put page flips etc. to system_unbound_wq
> allowing page flips on one pipe to execute in parallel with page flips
> or a modeset on a another pipe (assuming no known state is shared
> between them, at which point they would have been added to the same
> atomic commit and serialized that way).
>
> Blocking modesets are already serialized with each other by
> connection_mutex, and thus are safe. To serialize them with
> non-blocking modesets we just flush the workqueue before executing
> blocking modesets.
>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Fixes: 94f050246b42 ("drm/i915: nonblocking commit")
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
This patch won't really fix it, you could still have a blocking modeset in parallel to a nonblocking one. What would really be needed to fix those instances here?