Messages in this thread | | | Date | Wed, 23 Jul 2014 06:41:16 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 04/16] rcu: Remove redundant check for an online CPU |
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On Wed, Jul 23, 2014 at 09:23:47AM -0400, Pranith Kumar wrote: > On Wed, Jul 23, 2014 at 8:09 AM, Paul E. McKenney > <paulmck@linux.vnet.ibm.com> wrote: > > On Wed, Jul 23, 2014 at 01:09:41AM -0400, Pranith Kumar wrote: > >> rcu_prcess_callbacks() is the softirq handler for RCU which is raised from > >> invoke_rcu_core() which is called from __call_rcu_core(). > >> > >> Each of these three functions checks if the cpu is online. We can remove the > >> redundant ones. This commit removes one of these redundant check. > >> > >> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> > > > > Sorry, but no. There can be a long delay between raise_softirq() and > > this function starting, particularly if ksoftirqd gets involved. The > > CPU could easily go offline in the meantime. > > > > That makes sense. I guess one of the other two checks in > __call_rcu_core() or invoke_rcu_core() can go then?
What would have to be the case for this suggested change to be safe? Does that condition in fact hold?
Thanx, Paul
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