Messages in this thread | | | Date | Tue, 29 Nov 2011 01:26:01 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 1/4] rcu: Don't check irq nesting from rcu idle entry/exit |
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On Mon, Nov 28, 2011 at 04:22:44PM -0800, Paul E. McKenney wrote: > On Mon, Nov 28, 2011 at 10:24:44PM +0100, Frederic Weisbecker wrote: > > rcu_idle_enter() and rcu_idle_exit() don't need to check > > the irq nesting as they are not called from irq. > > > > Only check dyntick_nesting from rcu_irq_enter() and > > rcu_irq_exit(). > > > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > > Cc: Josh Triplett <josh@joshtriplett.org> > > --- > > kernel/rcutree.c | 18 ++++++++---------- > > 1 files changed, 8 insertions(+), 10 deletions(-) > > I have queued this. I had to update it to deal with a recent conflicting > update, please see below for the new version. > > Thanx, Paul
Hmm, seems there is a problem. Look below:
> > ------------------------------------------------------------------------ > > rcu: Don't check irq nesting from rcu idle entry/exit > > Because tasks do not nest, rcu_idle_enter() and rcu_idle_exit() do > not need to check for nesting. This commit therefore moves nesting > checks from rcu_idle_enter_common() to rcu_irq_exit() and from > rcu_idle_exit_common() to rcu_irq_enter(). > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > Cc: Josh Triplett <josh@joshtriplett.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index bf085d7..54d9b4f 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -350,10 +350,6 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp) > */ > static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval) > { > - if (rdtp->dynticks_nesting) { > - trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); > - return; > - } > trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting); > if (!is_idle_task(current)) { > struct task_struct *idle = idle_task(smp_processor_id()); > @@ -426,7 +422,10 @@ void rcu_irq_exit(void) > oldval = rdtp->dynticks_nesting; > rdtp->dynticks_nesting--; > WARN_ON_ONCE(rdtp->dynticks_nesting < 0); > - rcu_idle_enter_common(rdtp, oldval); > + if (rdtp->dynticks_nesting) > + trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); > + else > + rcu_idle_enter_common(rdtp, oldval); > local_irq_restore(flags); > } > > @@ -439,10 +438,6 @@ void rcu_irq_exit(void) > */ > static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) > { > - if (oldval) { > - trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); > - return; > - } > smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ > atomic_inc(&rdtp->dynticks); > /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ > @@ -519,6 +514,10 @@ void rcu_irq_enter(void) > rdtp->dynticks_nesting++; > WARN_ON_ONCE(rdtp->dynticks_nesting == 0); > rcu_idle_exit_common(rdtp, oldval);
It's now calling rcu_idle_exit_common twice?
> + if (oldval) > + trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); > + else > + rcu_idle_exit_common(rdtp, oldval); > local_irq_restore(flags); > } > >
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