| Date | Wed, 1 Feb 2012 17:01:46 -0800 | From | Josh Triplett <> | Subject | Re: [PATCH RFC tip/core/rcu 04/41] rcu: Add diagnostic for misaligned rcu_head structures |
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On Wed, Feb 01, 2012 at 11:41:22AM -0800, Paul E. McKenney wrote: > From: "Paul E. McKenney" <paul.mckenney@linaro.org> > > The push for energy efficiency will require that RCU tag rcu_head > structures to indicate whether or not their invocation is time critical. > This tagging is best carried out in the bottom bits of the ->next > pointers in the rcu_head structures. This tagging requires that the > rcu_head structures be properly aligned, so this commit adds the required > diagnostics. > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > kernel/rcutree.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index d0f8e64..4655f3e 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1707,6 +1707,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), > unsigned long flags; > struct rcu_data *rdp; > > + WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ > debug_rcu_head_queue(head);
Upon further checking:
static inline void debug_rcu_head_queue(struct rcu_head *head) { WARN_ON_ONCE((unsigned long)head & 0x3);
:)
- Josh Triplett
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