Messages in this thread |  | | Date | Mon, 3 Oct 2016 15:37:45 +0100 | From | Matt Fleming <> | Subject | Re: [PATCH v2 1/7] sched/fair: Update the rq clock before detaching tasks |
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On Mon, 03 Oct, at 02:49:07PM, Peter Zijlstra wrote: > On Wed, Sep 21, 2016 at 02:38:07PM +0100, Matt Fleming wrote: > > detach_task_cfs_rq() may indirectly call rq_clock() to inform the > > cpufreq code that the rq utilisation has changed. In which case, we > > need to update the rq clock. > > Hurm,. so it would've been good to know the callchain that got you > there. > > There's two functions that use detach_task_cfs_rq(), one is through > sched_change_group() and that does indeed lack a rq_clock update. > > The other is through switched_from() where its far harder (but still > possible afaict) to miss the update.
It was the former callchain.
> Now, neither cases are really fast paths, but it would be good to try > and avoid too many update_rq_clock() calls in the same rq-lock section. > So I'm not entirely sure about the placement here. > > But let me go stare at the actual debug framework thing first.. I think > this patch is fallout/fixups from that.
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