rcu: Repurpose no-CBs event tracing to future-GP events

Dyntick-idle CPUs need to be able to pre-announce their need for grace
periods.  This can be done using something similar to the mechanism used
by no-CB CPUs to announce their need for grace periods.  This commit
moves in this direction by renaming the no-CBs grace-period event tracing
to suit the new future-grace-period needs.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

include/trace/events/rcu.h

@@ -72,10 +72,10 @@ TRACE_EVENT(rcu_grace_period,
 );
 
 /*
- * Tracepoint for no-callbacks grace-period events.  The caller should
- * pull the data from the rcu_node structure, other than rcuname, which
- * comes from the rcu_state structure, and event, which is one of the
- * following:
+ * Tracepoint for future grace-period events, including those for no-callbacks
+ * CPUs.  The caller should pull the data from the rcu_node structure,
+ * other than rcuname, which comes from the rcu_state structure, and event,
+ * which is one of the following:
  *
  * "Startleaf": Request a nocb grace period based on leaf-node data.
  * "Startedleaf": Leaf-node start proved sufficient.
@@ -87,7 +87,7 @@ TRACE_EVENT(rcu_grace_period,
  * "Cleanup": Clean up rcu_node structure after previous GP.
  * "CleanupMore": Clean up, and another no-CB GP is needed.
  */
-TRACE_EVENT(rcu_nocb_grace_period,
+TRACE_EVENT(rcu_future_grace_period,
 
 	TP_PROTO(char *rcuname, unsigned long gpnum, unsigned long completed,
 		 unsigned long c, u8 level, int grplo, int grphi,
@@ -653,7 +653,7 @@ TRACE_EVENT(rcu_barrier,
 #define trace_rcu_grace_period(rcuname, gpnum, gpevent) do { } while (0)
 #define trace_rcu_grace_period_init(rcuname, gpnum, level, grplo, grphi, \
 				    qsmask) do { } while (0)
-#define trace_rcu_nocb_grace_period(rcuname, gpnum, completed, c, \
+#define trace_rcu_future_grace_period(rcuname, gpnum, completed, c, \
 				      level, grplo, grphi, event) \
 				      do { } while (0)
 #define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0)

kernel/rcutree_plugin.h

@@ -2034,7 +2034,7 @@ static int rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
 	wake_up_all(&rnp->nocb_gp_wq[c & 0x1]);
 	rnp->n_nocb_gp_requests[c & 0x1] = 0;
 	needmore = rnp->n_nocb_gp_requests[(c + 1) & 0x1];
-	trace_rcu_nocb_grace_period(rsp->name, rnp->gpnum, rnp->completed,
+	trace_rcu_future_grace_period(rsp->name, rnp->gpnum, rnp->completed,
 				      c, rnp->level, rnp->grplo, rnp->grphi,
 				      needmore ? "CleanupMore" : "Cleanup");
 	return needmore;
@@ -2183,9 +2183,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 
 	/* Count our request for a grace period. */
 	rnp->n_nocb_gp_requests[c & 0x1]++;
-	trace_rcu_nocb_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed,
-				    c, rnp->level, rnp->grplo, rnp->grphi,
-				    "Startleaf");
+	trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
+				      rnp->completed, c, rnp->level,
+				      rnp->grplo, rnp->grphi, "Startleaf");
 
 	if (rnp->gpnum != rnp->completed) {
 
@@ -2194,9 +2194,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 		 * is in progress, so we are done.  When this grace
 		 * period ends, our request will be acted upon.
 		 */
-		trace_rcu_nocb_grace_period(rdp->rsp->name,
-					    rnp->gpnum, rnp->completed, c,
-					    rnp->level, rnp->grplo, rnp->grphi,
+		trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
+					      rnp->completed, c, rnp->level,
+					      rnp->grplo, rnp->grphi,
 					      "Startedleaf");
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
@@ -2209,8 +2209,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 		if (rnp != rnp_root)
 			raw_spin_lock(&rnp_root->lock); /* irqs disabled. */
 		if (rnp_root->gpnum != rnp_root->completed) {
-			trace_rcu_nocb_grace_period(rdp->rsp->name,
-						    rnp->gpnum, rnp->completed,
+			trace_rcu_future_grace_period(rdp->rsp->name,
+						      rnp->gpnum,
+						      rnp->completed,
 						      c, rnp->level,
 						      rnp->grplo, rnp->grphi,
 						      "Startedleafroot");
@@ -2229,8 +2230,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 			c = rnp_root->completed + 1;
 			rnp->n_nocb_gp_requests[c & 0x1]++;
 			rnp_root->n_nocb_gp_requests[c & 0x1]++;
-			trace_rcu_nocb_grace_period(rdp->rsp->name,
-						    rnp->gpnum, rnp->completed,
+			trace_rcu_future_grace_period(rdp->rsp->name,
+						      rnp->gpnum,
+						      rnp->completed,
 						      c, rnp->level,
 						      rnp->grplo, rnp->grphi,
 						      "Startedroot");
@@ -2249,9 +2251,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 	 * Wait for the grace period.  Do so interruptibly to avoid messing
 	 * up the load average.
 	 */
-	trace_rcu_nocb_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed,
-				    c, rnp->level, rnp->grplo, rnp->grphi,
-				    "StartWait");
+	trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
+				      rnp->completed, c, rnp->level,
+				      rnp->grplo, rnp->grphi, "StartWait");
 	for (;;) {
 		wait_event_interruptible(
 			rnp->nocb_gp_wq[c & 0x1],
@@ -2259,14 +2261,14 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 		if (likely(d))
 			break;
 		flush_signals(current);
-		trace_rcu_nocb_grace_period(rdp->rsp->name,
+		trace_rcu_future_grace_period(rdp->rsp->name,
 					      rnp->gpnum, rnp->completed, c,
-					    rnp->level, rnp->grplo, rnp->grphi,
-					    "ResumeWait");
+					      rnp->level, rnp->grplo,
+					      rnp->grphi, "ResumeWait");
 	}
-	trace_rcu_nocb_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed,
-				    c, rnp->level, rnp->grplo, rnp->grphi,
-				    "EndWait");
+	trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
+				      rnp->completed, c, rnp->level,
+				      rnp->grplo, rnp->grphi, "EndWait");
 	smp_mb(); /* Ensure that CB invocation happens after GP end. */
 }