Re: [PATCH 04/16] rcu: Remove redundant check for an online CPU

Pranith Kumar
2014-07-23T13:24:21Z

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?

--
Pranith