Messages in this thread | | | Date | Wed, 8 Jun 2011 19:17:17 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH tip/core/rcu 03/28] rcu: Streamline code produced by __rcu_read_unlock() |
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* Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote: > Given some common flag combinations, particularly -Os, gcc will inline > rcu_read_unlock_special() despite its being in an unlikely() clause. > Use noline to prohibit this misoptimization.
noline -> noinline
> > In addition, move the second barrier() in __rcu_read_unlock() so that > it is not on the common-case code path. This will allow the compiler to > generate better code for the common-case path through __rcu_read_unlock(). > > Finally, fix up whitespace in kernel/lockdep.c to keep checkpatch happy.
This cleanup probably moved to a separate patch, but this comment line did not follow.
Other than that, feel free to add my
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > kernel/rcutree_plugin.h | 12 ++++++------ > 1 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > index ea2e2fb..40a6db7 100644 > --- a/kernel/rcutree_plugin.h > +++ b/kernel/rcutree_plugin.h > @@ -284,7 +284,7 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t, > * notify RCU core processing or task having blocked during the RCU > * read-side critical section. > */ > -static void rcu_read_unlock_special(struct task_struct *t) > +static noinline void rcu_read_unlock_special(struct task_struct *t) > { > int empty; > int empty_exp; > @@ -387,11 +387,11 @@ void __rcu_read_unlock(void) > struct task_struct *t = current; > > barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */ > - --t->rcu_read_lock_nesting; > - barrier(); /* decrement before load of ->rcu_read_unlock_special */ > - if (t->rcu_read_lock_nesting == 0 && > - unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) > - rcu_read_unlock_special(t); > + if (--t->rcu_read_lock_nesting == 0) { > + barrier(); /* decr before ->rcu_read_unlock_special load */ > + if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) > + rcu_read_unlock_special(t); > + } > #ifdef CONFIG_PROVE_LOCKING > WARN_ON_ONCE(ACCESS_ONCE(t->rcu_read_lock_nesting) < 0); > #endif /* #ifdef CONFIG_PROVE_LOCKING */ > -- > 1.7.3.2 >
-- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com
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