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[tip/core/rcu,19/23] rcu: Adjust for unconditional ->completed assignment

Message ID 1346350718-30937-19-git-send-email-paulmck@linux.vnet.ibm.com
State Superseded
Headers show

Commit Message

Paul E. McKenney Aug. 30, 2012, 6:18 p.m. UTC 
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

Now that the rcu_node structures' ->completed fields are unconditionally
assigned at grace-period cleanup time, they should already have the
correct value for the new grace period at grace-period initialization
time.  This commit therefore inserts a WARN_ON_ONCE() to verify this
invariant.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

Comments

Josh Triplett Sept. 3, 2012, 9:42 a.m. UTC | #1 
On Thu, Aug 30, 2012 at 11:18:34AM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> 
> Now that the rcu_node structures' ->completed fields are unconditionally
> assigned at grace-period cleanup time, they should already have the
> correct value for the new grace period at grace-period initialization
> time.  This commit therefore inserts a WARN_ON_ONCE() to verify this
> invariant.
> 
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Reviewed-by: Josh Triplett <josh@joshtriplett.org>

>  kernel/rcutree.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index 1373388..86903df 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -1098,6 +1098,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
>  		rcu_preempt_check_blocked_tasks(rnp);
>  		rnp->qsmask = rnp->qsmaskinit;
>  		rnp->gpnum = rsp->gpnum;
> +		WARN_ON_ONCE(rnp->completed != rsp->completed);
>  		rnp->completed = rsp->completed;
>  		if (rnp == rdp->mynode)
>  			rcu_start_gp_per_cpu(rsp, rnp, rdp);
> @@ -2795,7 +2796,8 @@ static void __init rcu_init_one(struct rcu_state *rsp,
>  			raw_spin_lock_init(&rnp->fqslock);
>  			lockdep_set_class_and_name(&rnp->fqslock,
>  						   &rcu_fqs_class[i], fqs[i]);
> -			rnp->gpnum = 0;
> +			rnp->gpnum = rsp->gpnum;
> +			rnp->completed = rsp->completed;
>  			rnp->qsmask = 0;
>  			rnp->qsmaskinit = 0;
>  			rnp->grplo = j * cpustride;
> -- 
> 1.7.8
>
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Patch

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 1373388..86903df 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1098,6 +1098,7 @@  static int rcu_gp_init(struct rcu_state *rsp)
 		rcu_preempt_check_blocked_tasks(rnp);
 		rnp->qsmask = rnp->qsmaskinit;
 		rnp->gpnum = rsp->gpnum;
+		WARN_ON_ONCE(rnp->completed != rsp->completed);
 		rnp->completed = rsp->completed;
 		if (rnp == rdp->mynode)
 			rcu_start_gp_per_cpu(rsp, rnp, rdp);
@@ -2795,7 +2796,8 @@  static void __init rcu_init_one(struct rcu_state *rsp,
 			raw_spin_lock_init(&rnp->fqslock);
 			lockdep_set_class_and_name(&rnp->fqslock,
 						   &rcu_fqs_class[i], fqs[i]);
-			rnp->gpnum = 0;
+			rnp->gpnum = rsp->gpnum;
+			rnp->completed = rsp->completed;
 			rnp->qsmask = 0;
 			rnp->qsmaskinit = 0;
 			rnp->grplo = j * cpustride;