Messages in this thread |  | | | Date | Thu, 21 Sep 2006 09:16:24 +0200 | | From | Ingo Molnar <> | | Subject | Re: [PATCH] move put_task_struct() reaping into a thread [Re: 2.6.18-rt1] |
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* Bill Huey <billh@gnuppy.monkey.org> wrote:
> > > This patch moves put_task_struct() reaping into a thread instead > > > of an RCU callback function [...] > > > > had some time to think about it since yesterday: RCU reaping is done > > in softirqs (check out the softirq-rcu threads on your -rt box), > > that's why i removed the delayed-task-drop code to begin with. Now i > > dont doubt > > It's correct from the standpoint of it being reaped in another thread, > so it fixed those crashes. But I pushed it down into another thread at > the request of Esben and his private discussion with Paul McKenney, > since a summary from Esben felt that call_rcu() was somehow less than > ideal to do that.
but it _is_ already being reaped in another thread: softirq-rcu. Splitting that up any further will only fragment the context-switching and increases cache footprint - it wont (or rather, shouldnt) have any functional effect. (As a sidenote, i'm considering the unification of all 'same default priority' softirq threads into a single thread per CPU, to further reduce this cost of 'spreadout'.)
> > that you saw crashes under 2.6.17 - but did you manage to figure out > > what the reason is for those crashes, and do those reasons really > > necessiate the pushing of task-reapdown into yet another set of > > kernel threads? > > Unfortunately no. I even used Robert's .config on my machine. I added > a disk controller and networking device driver just to boot into his > configuration and I still couldn't replicated any of his kjournald > problems at all. If I had his hardware I'd have a better way of > replicating those problems and pound it out.
ok, then i guess what we have left is to wait and see whether it still triggers with the current 2.6.18-rt codebase - maybe it triggers for someone in a scenario that is easier to debug.
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