Messages in this thread | | | Date | Fri, 15 Jun 2012 18:01:49 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 13/15] rcu: Introduce for_each_rcu_flavor() and use it |
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On Fri, Jun 15, 2012 at 04:52:40PM -0700, Josh Triplett wrote: > On Fri, Jun 15, 2012 at 02:06:08PM -0700, Paul E. McKenney wrote: > > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > > > > The arrival of TREE_PREEMPT_RCU some years back included some ugly > > code involving either #ifdef or #ifdef'ed wrapper functions to iterate > > over all non-SRCU flavors of RCU. This commit therefore introduces > > a for_each_rcu_flavor() iterator over the rcu_state structures for each > > flavor of RCU to clean up a bit of the ugliness. > > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Great cleanup! > > A few comments below, though. > > > kernel/rcutree.c | 53 +++++++++++++--------- > > kernel/rcutree.h | 12 ++--- > > kernel/rcutree_plugin.h | 116 ----------------------------------------------- > > 3 files changed, 36 insertions(+), 145 deletions(-) > > Awesome diffstat.
;-)
> > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > > index bd4e41c..75ad92a 100644 > > --- a/kernel/rcutree.c > > +++ b/kernel/rcutree.c > > @@ -84,6 +84,7 @@ struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh); > > DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); > > > > static struct rcu_state *rcu_state; > > +LIST_HEAD(rcu_struct_flavors); > > Does any means exist to turn this into a constant array known at compile > time rather than a runtime linked list? Having this as a compile-time > constant may allow the compiler to unroll for_each_rcu_flavor and > potentially inline the calls inside it.
I could do that, but none of the traversals is anywhere near performance critical, and all the ways I can think of to do this are uglier than the list.
> > @@ -2539,9 +2548,10 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) > > > > static void __cpuinit rcu_prepare_cpu(int cpu) > > { > > - rcu_init_percpu_data(cpu, &rcu_sched_state, 0); > > - rcu_init_percpu_data(cpu, &rcu_bh_state, 0); > > - rcu_preempt_init_percpu_data(cpu); > > + struct rcu_state *rsp; > > + > > + for_each_rcu_flavor(rsp) > > + rcu_init_percpu_data(cpu, rsp, 0); > > This results in passing 0 as the "preemptible" parameter of > rcu_init_percpu_data, which seems wrong if the preemptible parameter has > any meaning at all. :)
Good catch! Hmmm... Probably best to move this to the rcu_state initialization.
> > @@ -2577,18 +2588,15 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, > > * touch any data without introducing corruption. We send the > > * dying CPU's callbacks to an arbitrarily chosen online CPU. > > */ > > - rcu_cleanup_dying_cpu(&rcu_bh_state); > > - rcu_cleanup_dying_cpu(&rcu_sched_state); > > - rcu_preempt_cleanup_dying_cpu(); > > - rcu_cleanup_after_idle(cpu); > > + for_each_rcu_flavor(rsp) > > + rcu_cleanup_dying_cpu(rsp); > > Why did rcu_cleanup_after_idle go away here?
Because I fat-fingered it. Thank you very much for spotting this. It would have been nasty to find otherwise.
Thanx, Paul
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