[Bug 25017] computer fails to suspend with kms enabled.

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=25017


Nix <nix at esperi.org.uk> changed:

           What    |Removed                     |Added
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                 CC|                            |nix at esperi.org.uk




--- Comment #1 from Nix <nix at esperi.org.uk>  2009-11-10 16:20:30 PST ---
It's certainly not completely broken: for me, with an HD4870, KMS suspension
(with TuxOnIce) mostly works better than non-KMS --- non-KMS locked up on
resume unless I switched to text mode before suspending.


But there is *one* possible problem: I haven't yet isolated it to KMS
definitively, I'm just suspicious, so this is just a heads-up.

TuxOnIce starts out with a limited set of reserved pages which are not
atomically copied, for drivers to use during suspension, but (unlike with the
in-tree swsusp, IIRC) this is not a hard limit. Radeon KMS touches a *lot* of
pages during suspension if 3D has ever been used: I've seen figures upwards of
38000 (!!) at times, even if 3D's not in use at suspension time. If we run out,
TOI recovers, expands the reserved set, and tries to copy again; as this
involves allocation of (possibly much) more storage, we thaw processes and
refreeze them after the allocation. This means that a freeze is not always
followed by hibernation, but may be followed by a thaw and another freeze.

Radeon KMS seems to dislike this: for me, at least, this freeze/thaw/freeze
cycle results in a lockup if KMS is running.

(As I said earlier, I haven't yet isolated it to KMS in particular. Without KMS
running, no drivers on my system need any reserved pages at all, so the
freeze/thaw/freeze cycle is never initiated, and I always get away with a
single freeze round; equally, if I arrange to allocate enough reserved pages
with KMS running, it suspends and resumes perfectly. So this may be a false
alarm: some other driver may be at fault.)


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