Messages in this thread | | | Date | Tue, 22 Mar 2011 23:35:24 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 8/9] jrcu: fix broken rcu_barrier |
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On Mon, Mar 14, 2011 at 06:09:28PM -0400, Joe Korty wrote: > On Mon, Mar 14, 2011 at 04:47:18AM -0400, Paul E. McKenney wrote: > > On Sun, Mar 13, 2011 at 11:50:44PM -0400, Joe Korty wrote: > > > +void rcu_barrier(void) > > > +{ > > > + synchronize_sched(); > > > + synchronize_sched(); > > > +} > > > > This is still broken. You need to wait until all pre-existing RCU > > callbacks on all CPUs have been invoked. Although this does guarantee > > that all callbacks on the current CPU have been invoked, if one of the > > other CPUs is busy, it might not yet have processed the callbacks from > > earlier grace periods. The usual way to take care of this is to post > > a callback on each CPU, then wait for them all to be invoked. > > Hi Paul, > JRCU (eventually) chains together all callbacks from all > cpus into a single queue and then it expires that single > queue. So the double synchronize_sched() should work as > a rcu_barrier implementation.
Hello, Joe,
So the following grace period is not permitted to start until all of the callbacks from the prior grace period have been invoked?
Or am I missing something subtle here?
Thanx, Paul
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