[Bug 109606] [CI][DRMTIP] igt at pm_rps@reset - dmesg-fail - Failed assertion: __gem_execbuf_wr(fd, execbuf) == 0

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109606

--- Comment #5 from Martin Peres <martin.peres at free.fr> ---
(In reply to Chris Wilson from comment #4)
> commit 89531e7d8ee8602b2723431a581250d5d0ec2913
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Tue Feb 26 09:49:19 2019 +0000
> 
>     drm/i915: Replace global_seqno with a hangcheck heartbeat seqno
>     
>     To determine whether an engine has 'stuck', we simply check whether or
>     not is still on the same seqno for several seconds. To keep this simple
>     mechanism intact over the loss of a global seqno, we can simply add a
>     new global heartbeat seqno instead. As we cannot know the sequence in
>     which requests will then be completed, we use a primitive random number
>     generator instead (with a cycle long enough to not matter over an
>     interval of a few thousand requests between hangcheck samples).
>     
>     The alternative to using a dedicated seqno on every request is to issue
>     a heartbeat request and query its progress through the system. Sadly
>     this requires us to reduce struct_mutex so that we can issue requests
>     without requiring that bkl.
>     
>     v2: And without the extra CS_STALL for the hangcheck seqno -- we don't
>     need strict serialisation with what comes later, we just need to be sure
>     we don't write the hangcheck seqno before our batch is flushed.
>     
>     Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>     Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>     Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>     Link:
> https://patchwork.freedesktop.org/patch/msgid/20190226094922.31617-1-
> chris at chris-wilson.co.uk

Fair-enough! Thanks!

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