Messages in this thread | | | Date | Fri, 21 Jan 2011 05:31:53 +1100 | Subject | Re: [patch] fs: aio fix rcu lookup | From | Nick Piggin <> |
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On Thu, Jan 20, 2011 at 3:03 PM, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > On Thu, Jan 20, 2011 at 08:20:00AM +1100, Nick Piggin wrote: >> On Thu, Jan 20, 2011 at 8:03 AM, Jeff Moyer <jmoyer@redhat.com> wrote: >> >> I don't know exactly how all programs use io_destroy -- of the small >> >> number that do, probably an even smaller number would care here. But I >> >> don't think it simplifies things enough to use synchronize_rcu for it. >> > >> > Above it sounded like you didn't think AIO should be using RCU at all. >> >> synchronize_rcu of course, not RCU (typo). > > I think that Nick is suggesting that call_rcu() be used instead. > Perhaps also very sparing use of synchronize_rcu_expedited(), which > is faster than synchronize_rcu(), but which which uses more CPU time.
call_rcu() is the obvious alternative, yes.
Basically, once we give in to synchronize_rcu() we're basically giving up. That's certainly a very good tradeoff for something like filesystem unregistration or module unload, it buys big simplifications in real fastpaths. But I just don't think it should be taken lightly.
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