From: Daniel Stone <daniel@fooishbar.org>
To: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>,
ML dri-devel <dri-devel@lists.freedesktop.org>,
Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [Intel-gfx] sw_sync deadlock avoidance, take 3
Date: Wed, 15 Jul 2020 12:47:15 +0100 [thread overview]
Message-ID: <CAPj87rN+Sg6PRzGx-FjRFBoenpD9EsV9=ZbiCHEThcgt09YbMQ@mail.gmail.com> (raw)
In-Reply-To: <CAP+8YyHDYQSBmRohBwnhcB96p+ZHU2hT106CS6_-8A0Fk1Hegw@mail.gmail.com>
Hi,
On Wed, 15 Jul 2020 at 12:05, Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl> wrote:
> On Wed, Jul 15, 2020 at 12:34 PM Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > Maybe now is the time to ask: are you using sw_sync outside of
> > validation?
>
> Yes, this is used as part of the Android stack on Chrome OS (need to
> see if ChromeOS specific, but
> https://source.android.com/devices/graphics/sync#sync_timeline
> suggests not)
Android used to mandate it for their earlier iteration of release
fences, which was an empty/future fence having no guarantee of
eventual forward progress until someone committed work later on. For
example, when you committed a buffer to SF, it would give you an empty
'release fence' for that buffer which would only be tied to work to
signal it when you committed your _next_ buffer, which might never
happen. They removed that because a) future fences were a bad idea,
and b) it was only ever useful if you assumed strictly
FIFO/round-robin return order which wasn't always true.
So now it's been watered down to 'use this if you don't have a
hardware timeline', but why don't we work with Android people to get
that removed entirely?
Cheers,
Daniel
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next prev parent reply other threads:[~2020-07-15 11:47 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 10:04 sw_sync deadlock avoidance, take 3 Chris Wilson
2020-07-15 10:04 ` [PATCH 1/2] dma-buf/sw_sync: Avoid recursive lock during fence signal Chris Wilson
2020-07-15 11:26 ` Bas Nieuwenhuizen
2020-07-15 10:04 ` [PATCH 2/2] dma-buf/selftests: Add locking selftests for sw_sync Chris Wilson
2020-07-15 10:23 ` sw_sync deadlock avoidance, take 3 Bas Nieuwenhuizen
2020-07-15 10:29 ` Daniel Stone
2020-07-15 10:34 ` Chris Wilson
2020-07-15 11:05 ` Bas Nieuwenhuizen
2020-07-15 11:47 ` Daniel Stone [this message]
2020-07-15 11:57 ` [Intel-gfx] " Daniel Vetter
2020-07-17 0:24 ` Daniel Stone
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