Arjan van de Ven wrote:
> On Thu, 15 Nov 2007 04:00:47 GMT
> Linux Kernel Mailing List <[email protected]> wrote:
>
>
>> Gitweb:
>> http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=35d5d08a085c56f153458c3f5d8ce24123617faf
>> Commit: 35d5d08a085c56f153458c3f5d8ce24123617faf Parent:
>> 7eea436433b7b18045f272562e256976f593f7c0 Author: Andrew Morton
>> <[email protected]> AuthorDate: Wed Nov 14 17:00:41 2007 -0800
>> Committer: Linus Torvalds <[email protected]>
>> CommitDate: Wed Nov 14 18:45:44 2007 -0800
>>
>> x86: disable preemption in delay_tsc()
>>
>> Marin Mitov points out that delay_tsc() can misbehave if it is
>> preempted and rescheduled on a different CPU which has a skewed TSC.
>> Fix it by disabling preemption.
>>
>>
>
> this worries me.. this appears to effectively disable preemption during
> udelay() and mdelay() loops... which are very obvious latency inducers.
>
> Now you can argue that if you're preemptible you should have used
> msleep() and co, and I'll totally buy that.
>
>
> Maybe we should just check if we're still on the same cpu or something,
> or have a cheap way to pin a process to a cpu.... but both are longer
> term solutions.
>
>
You can use preemption notifiers to get a callback when you are
preempted. Not sure what you'd to with that callback, though.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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