Messages in this thread | | | Date | Tue, 10 Jan 2006 23:43:31 +0530 | From | Dipankar Sarma <> | Subject | Re: [PATCH 2/5] rcu: don't check ->donelist in __rcu_pending() |
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On Sun, Jan 08, 2006 at 10:19:24PM +0300, Oleg Nesterov wrote: > ->donelist becomes != NULL only in rcu_process_callbacks(). > > So ->donelist != NULL means that rcu_tasklet is either > TASKLET_STATE_SCHED or TASKLET_STATE_RUN, we don't need to > check it in __rcu_pending(). > > [ This patch was tested with rcutorture.ko, I don't understand > it's output, but it says "End of test: SUCCESS". So if this > patch incorrect blame Paul, not me! ] > > Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> > > --- 2.6.15/kernel/rcupdate.c~2_DONE 2006-01-08 21:35:21.000000000 +0300 > +++ 2.6.15/kernel/rcupdate.c 2006-01-08 21:55:45.000000000 +0300 > @@ -454,10 +454,6 @@ static int __rcu_pending(struct rcu_ctrl > if (!rdp->curlist && rdp->nxtlist) > return 1; > > - /* This cpu has finished callbacks to invoke */ > - if (rdp->donelist) > - return 1; > - > /* The rcu core waits for a quiescent state from the cpu */ > if (rdp->quiescbatch != rcp->cur || rdp->qs_pending) > return 1;
This may not be a good idea. For example, during cpu hotplug, a cpu may inherit a set of finished callbacks that need to be invoked. So, an rcu_pending() check needs to detect that.
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