Messages in this thread | | | Date | Tue, 7 Jun 2011 10:26:06 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] sched: remove rcu_read_lock from wake_affine |
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On Tue, Jun 07, 2011 at 12:26:51PM +0200, Peter Zijlstra wrote: > On Tue, 2011-06-07 at 15:43 +0530, Nikunj A. Dadhania wrote: > > wake_affine is called from one path: select_task_rq_fair, which already has > > rcu read lock held. > > > > Signed-off-by: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com> > > --- > > kernel/sched_fair.c | 3 +-- > > 1 files changed, 1 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > > index 354e26b..0bfec93 100644 > > --- a/kernel/sched_fair.c > > +++ b/kernel/sched_fair.c > > @@ -1461,6 +1461,7 @@ static inline unsigned long effective_load(struct task_group *tg, int cpu, > > > > #endif > > > > +/* Assumes rcu_read_lock is held */ > > Not a big fan of such comments, esp with CONFIG_PROVE_RCU its better to > use those facilities, which is to say: if we're missing a > rcu_read_lock() the thing will yell bloody murder.
Nikunj, one such approach is is "WARN_ON_ONCE(!rcu_read_lock_held())".
This will complain if this function is called without an rcu_read_lock() in effect, but only if CONFIG_PROVE_RCU=y.
Thanx, Paul
> > static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) > > { > > s64 this_load, load; > > @@ -1481,7 +1482,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) > > * effect of the currently running task from the load > > * of the current CPU: > > */ > > - rcu_read_lock(); > > if (sync) { > > tg = task_group(current); > > weight = current->se.load.weight; > > @@ -1517,7 +1517,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) > > balanced = this_eff_load <= prev_eff_load; > > } else > > balanced = true; > > - rcu_read_unlock(); > > > > /* > > * If the currently running task will sleep within > > > > OK, took the patch and removed the comment, thanks! > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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