Re: lots of brief rcu stalls.

Joe Perches
2013-12-05T02:36:13Z

On Wed, 2013-12-04 at 18:18 -0800, Eric Dumazet wrote:
> On Wed, 2013-12-04 at 16:16 -0800, Paul E. McKenney wrote:
> > + ULONG_CMP_GE(ACCESS_ONCE(jiffies), rdp->rsp->jiffies_resched)) {

perhaps time_before_eq

> jiffies should not need ACCESS_ONCE(), right ?
>
> It is one of the few variables marked with volatile keyword.

It does seem redundant

$ git grep -n "ACCESS_ONCE(jiffies)"
kernel/rcu/torture.c:1354: jiffies_snap = ACCESS_ONCE(jiffies);
kernel/rcu/torture.c:1363: jiffies_snap = ACCESS_ONCE(jiffies);
kernel/rcu/tree.c:820: unsigned long j = ACCESS_ONCE(jiffies);
kernel/rcu/tree.c:975: j = ACCESS_ONCE(jiffies);
kernel/sched/core.c:2324: unsigned long next, now = ACCESS_ONCE(jiffies);
kernel/sched/proc.c:536: unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
kernel/sched/proc.c:558: unsigned long curr_jiffies = ACCESS_ONCE(jiffies);