rcu: Further cleanups of use of lastcomp

Now that a copy of the rsp->completed flag is available in all
rcu_node structures, make full use of it.  It is still
legitimate to access rsp->completed while holding the root
rcu_node structure's lock, however.

Also, tighten up force_quiescent_state()'s checks for end of
current grace period.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1258170699933-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 7 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 3df04381ea3e..24bbf2ce0605 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -817,7 +817,7 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
 
         rnp = rdp->mynode;
         spin_lock_irqsave(&rnp->lock, flags);
-        if (lastcomp != ACCESS_ONCE(rsp->completed)) {
+        if (lastcomp != rnp->completed) {
 
                 /*
                  * Someone beat us to it for this grace period, so leave.
@@ -935,7 +935,6 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
 static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
 {
         unsigned long flags;
-        long lastcomp;
         unsigned long mask;
         struct rcu_data *rdp = rsp->rda[cpu];
         struct rcu_node *rnp;
@@ -971,7 +970,6 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
                 spin_unlock(&rnp->lock);        /* irqs remain disabled. */
                 rnp = rnp->parent;
         } while (rnp != NULL);
-        lastcomp = rsp->completed;
 
         spin_unlock_irqrestore(&rsp->onofflock, flags);
 
@@ -1145,7 +1143,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
         rcu_for_each_leaf_node(rsp, rnp) {
                 mask = 0;
                 spin_lock_irqsave(&rnp->lock, flags);
-                if (rsp->completed != lastcomp) {
+                if (rnp->completed != lastcomp) {
                         spin_unlock_irqrestore(&rnp->lock, flags);
                         return 1;
                 }
@@ -1159,7 +1157,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
                         if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
                                 mask |= bit;
                 }
-                if (mask != 0 && rsp->completed == lastcomp) {
+                if (mask != 0 && rnp->completed == lastcomp) {
 
                         /* cpu_quiet_msk() releases rnp->lock. */
                         cpu_quiet_msk(mask, rsp, rnp, flags);
@@ -1196,7 +1194,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
         lastcomp = rsp->gpnum - 1;
         signaled = rsp->signaled;
         rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
-        if (lastcomp == rsp->gpnum) {
+        if(!rcu_gp_in_progress(rsp)) {
                 rsp->n_force_qs_ngp++;
                 spin_unlock(&rnp->lock);
                 goto unlock_ret;  /* no GP in progress, time updated. */
@@ -1224,7 +1222,8 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
                 /* Update state, record completion counter. */
                 forcenow = 0;
                 spin_lock(&rnp->lock);
-                if (lastcomp == rsp->completed &&
+                if (lastcomp + 1 == rsp->gpnum &&
+                    lastcomp == rsp->completed &&
                     rsp->signaled == signaled) {
                         rsp->signaled = RCU_FORCE_QS;
                         rsp->completed_fqs = lastcomp;