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Date: Thu, 2 Feb 2012 08:27:55 -0800 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Josh Triplett <josh@...htriplett.org> Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com, fweisbec@...il.com, patches@...aro.org, "Paul E. McKenney" <paul.mckenney@...aro.org> Subject: Re: [PATCH RFC tip/core/rcu 04/41] rcu: Add diagnostic for misaligned rcu_head structures On Wed, Feb 01, 2012 at 05:01:46PM -0800, Josh Triplett wrote: > On Wed, Feb 01, 2012 at 11:41:22AM -0800, Paul E. McKenney wrote: > > From: "Paul E. McKenney" <paul.mckenney@...aro.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@...aro.org> > > Signed-off-by: Paul E. McKenney <paulmck@...ux.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); > > :) Fair point! I guess that we really only need one of these. ;-) I have kept the unconditional one and removed the one hidden under CONFIG_DEBUG_OBJECTS_RCU_HEAD, but in a separate commit with your Reported-by. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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