Messages in this thread | | | Date | Thu, 14 Jun 2012 07:50:38 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [RFC patch 2/5] smpboot: Provide infrastructure for percpu hotplug threads |
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On Thu, Jun 14, 2012 at 03:32:19PM +0200, Thomas Gleixner wrote: > On Thu, 14 Jun 2012, Paul E. McKenney wrote: > > On Thu, Jun 14, 2012 at 01:20:39PM +0200, Thomas Gleixner wrote: > > > I gave it a quick shot, but I was not able to reproduce the hang yet. > > > > Really? I have a strictly Western-Hemisphere bug? ;-) > > I guess I need to fire up rcu torture to make it surface.
A simple offline was triggering it for me. Perhaps some of my debug code was inappropriate, will retry.
> > > But looking at the thread function made me look into rcu_yield() and I > > > really wonder what kind of drug induced that particular piece of > > > horror. > > > > When you are working on something like RCU priority boosting, no other > > drug is in any way necessary. ;-) > > And how do we protect minors from that ?
We rely on their own sense of self-preservation preventing them from getting involved in such insanity.
> > > I can't figure out why this yield business is necessary at all. The > > > commit logs are as helpful as the missing code comments :) > > > > > > I suspect that it's some starvation issue. But if we need it, then > > > can't we replace it with something sane like the (untested) patch > > > below? > > > > Yep, starvation. I will take a look at your approach after I wake > > up a bit more. > > Btw, if that simpler yield approach is working and I can't see why it > shouldn't then you can get rid of the node task as well. The only > purpose of it is to push up the priority of yielding tasks, right?
It also boosts the priority of preempted RCU read-side critical sections.
Thanx, Paul
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