[PATCH] sched_clock: prevent scd->clock from moving backwards,take #2

[Ingo Molnar]

* Jayson King <dev@xxxxxxxxxxxxxx> wrote:

> Greetings,
>
> I noticed large latency spikes in 2.6.28 (and 2.6.27.10) which would 
> make the system unresponsive for minutes at a time (alt+Fn switching 
> wouldn't even work) when the system is under load. I could trigger the 
> latency by running a large make -j 3. Sometimes it would trigger in a 
> few seconds other times it would take a few minutes.
>
> I bisected it in 2.6.27.10 to d9a888b061f55534016d2d86a21639948312a117 
> -> Revert "sched_clock: prevent scd->clock from moving backwards" 
> (ca7e716c7833aeaeb8fedd6d004c5f5d5e14d325 in 2.6.28) and reverting it in 
> 2.6.28 make the latency spike go away. At least, so far no spike in over 
> 24 hours.

Could you try the patch below - does it solve the problem? (and if it 
solves the problem, and if you have working suspend-to-ram or hibernation 
on your system then please also double-check that those still work.)

	Ingo

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