4 files changed, 16 insertions, 27 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index a2eadd04fb29..6194402ec853 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -176,8 +176,6 @@ void rcu_sched_qs(int cpu)
 {
         struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
 
-        rdp->passed_quiesce_gpnum = rdp->gpnum;
-        barrier();
         if (rdp->passed_quiesce == 0)
                 trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
         rdp->passed_quiesce = 1;
@@ -187,8 +185,6 @@ void rcu_bh_qs(int cpu)
 {
         struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
 
-        rdp->passed_quiesce_gpnum = rdp->gpnum;
-        barrier();
         if (rdp->passed_quiesce == 0)
                 trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
         rdp->passed_quiesce = 1;
@@ -899,12 +895,8 @@ static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct
                  */
                 rdp->gpnum = rnp->gpnum;
                 trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
-                if (rnp->qsmask & rdp->grpmask) {
-                        rdp->qs_pending = 1;
-                        rdp->passed_quiesce = 0;
-                } else {
-                        rdp->qs_pending = 0;
-                }
+                rdp->passed_quiesce = 0;
+                rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
                 zero_cpu_stall_ticks(rdp);
         }
 }
@@ -984,10 +976,13 @@ __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat
                  * our behalf. Catch up with this state to avoid noting
                  * spurious new grace periods.  If another grace period
                  * has started, then rnp->gpnum will have advanced, so
-                 * we will detect this later on.
+                 * we will detect this later on.  Of course, any quiescent
+                 * states we found for the old GP are now invalid.
                  */
-                if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
+                if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) {
                         rdp->gpnum = rdp->completed;
+                        rdp->passed_quiesce = 0;
+                }
 
                 /*
                  * If RCU does not need a quiescent state from this CPU,
@@ -1358,7 +1353,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
  * based on quiescent states detected in an earlier grace period!
  */
 static void
-rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp)
+rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 {
         unsigned long flags;
         unsigned long mask;
@@ -1366,7 +1361,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long las
 
         rnp = rdp->mynode;
         raw_spin_lock_irqsave(&rnp->lock, flags);
-        if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) {
+        if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum ||
+            rnp->completed == rnp->gpnum) {
 
                 /*
                  * The grace period in which this quiescent state was
@@ -1425,7 +1421,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
          * Tell RCU we are done (but rcu_report_qs_rdp() will be the
          * judge of that).
          */
-        rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum);
+        rcu_report_qs_rdp(rdp->cpu, rsp, rdp);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -2600,7 +2596,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
                         rdp->completed = rnp->completed;
                         rdp->passed_quiesce = 0;
                         rdp->qs_pending = 0;
-                        rdp->passed_quiesce_gpnum = rnp->gpnum - 1;
                         trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
                 }
                 raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 8f0293ce1517..935dd4ca6816 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -246,8 +246,6 @@ struct rcu_data {
                                         /*  in order to detect GP end. */
         unsigned long   gpnum;          /* Highest gp number that this CPU */
                                         /*  is aware of having started. */
-        unsigned long   passed_quiesce_gpnum;
-                                        /* gpnum at time of quiescent state. */
         bool            passed_quiesce; /* User-mode/idle loop etc. */
         bool            qs_pending;     /* Core waits for quiesc state. */
         bool            beenonline;     /* CPU online at least once. */
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index b4e8eb24a5f1..4734afbea73a 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -137,8 +137,6 @@ static void rcu_preempt_qs(int cpu)
 {
         struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
 
-        rdp->passed_quiesce_gpnum = rdp->gpnum;
-        barrier();
         if (rdp->passed_quiesce == 0)
                 trace_rcu_grace_period("rcu_preempt", rdp->gpnum, "cpuqs");
         rdp->passed_quiesce = 1;
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index f54f0ceda0cf..bd4df13d4afb 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -86,12 +86,11 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
 {
         if (!rdp->beenonline)
                 return;
-        seq_printf(m, "%3d%cc=%lu g=%lu pq=%d pgp=%lu qp=%d",
+        seq_printf(m, "%3d%cc=%lu g=%lu pq=%d qp=%d",
                    rdp->cpu,
                    cpu_is_offline(rdp->cpu) ? '!' : ' ',
                    rdp->completed, rdp->gpnum,
-                   rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
-                   rdp->qs_pending);
+                   rdp->passed_quiesce, rdp->qs_pending);
         seq_printf(m, " dt=%d/%llx/%d df=%lu",
                    atomic_read(&rdp->dynticks->dynticks),
                    rdp->dynticks->dynticks_nesting,
@@ -150,12 +149,11 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
 {
         if (!rdp->beenonline)
                 return;
-        seq_printf(m, "%d,%s,%lu,%lu,%d,%lu,%d",
+        seq_printf(m, "%d,%s,%lu,%lu,%d,%d",
                    rdp->cpu,
                    cpu_is_offline(rdp->cpu) ? "\"N\"" : "\"Y\"",
                    rdp->completed, rdp->gpnum,
-                   rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
-                   rdp->qs_pending);
+                   rdp->passed_quiesce, rdp->qs_pending);
         seq_printf(m, ",%d,%llx,%d,%lu",
                    atomic_read(&rdp->dynticks->dynticks),
                    rdp->dynticks->dynticks_nesting,
@@ -186,7 +184,7 @@ static int show_rcudata_csv(struct seq_file *m, void *unused)
         int cpu;
         struct rcu_state *rsp;
 
-        seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pgp\",\"pq\",");
+        seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pq\",");
         seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
         seq_puts(m, "\"of\",\"qll\",\"ql\",\"qs\"");
 #ifdef CONFIG_RCU_BOOST