rcu: Add event tracing for no-CBs CPUs' grace periods

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

2 files changed, 85 insertions, 0 deletions

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 1918e832da4f..cdfed6d386eb 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -72,6 +72,58 @@ 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:
+ *
+ * "Startleaf": Request a nocb grace period based on leaf-node data.
+ * "Startedleaf": Leaf-node start proved sufficient.
+ * "Startedleafroot": Leaf-node start proved sufficient after checking root.
+ * "Startedroot": Requested a nocb grace period based on root-node data.
+ * "StartWait": Start waiting for the requested grace period.
+ * "ResumeWait": Resume waiting after signal.
+ * "EndWait": Complete wait.
+ * "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,
+
+        TP_PROTO(char *rcuname, unsigned long gpnum, unsigned long completed,
+                 unsigned long c, u8 level, int grplo, int grphi,
+                 char *gpevent),
+
+        TP_ARGS(rcuname, gpnum, completed, c, level, grplo, grphi, gpevent),
+
+        TP_STRUCT__entry(
+                __field(char *, rcuname)
+                __field(unsigned long, gpnum)
+                __field(unsigned long, completed)
+                __field(unsigned long, c)
+                __field(u8, level)
+                __field(int, grplo)
+                __field(int, grphi)
+                __field(char *, gpevent)
+        ),
+
+        TP_fast_assign(
+                __entry->rcuname = rcuname;
+                __entry->gpnum = gpnum;
+                __entry->completed = completed;
+                __entry->c = c;
+                __entry->level = level;
+                __entry->grplo = grplo;
+                __entry->grphi = grphi;
+                __entry->gpevent = gpevent;
+        ),
+
+        TP_printk("%s %lu %lu %lu %u %d %d %s",
+                  __entry->rcuname, __entry->gpnum, __entry->completed,
+                  __entry->c, __entry->level, __entry->grplo, __entry->grphi,
+                  __entry->gpevent)
+);
+
+/*
  * Tracepoint for grace-period-initialization events.  These are
  * distinguished by the type of RCU, the new grace-period number, the
  * rcu_node structure level, the starting and ending CPU covered by the
@@ -601,6 +653,9 @@ 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, \
+                                    level, grplo, grphi, event) \
+                                    do { } while (0)
 #define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0)
 #define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
 #define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, \
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 7225a5a14cef..e32236e83dda 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2201,6 +2201,9 @@ 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,
+                                    c, rnp->level, rnp->grplo, rnp->grphi,
+                                    needmore ? "CleanupMore" : "Cleanup");
         return needmore;
 }
 
@@ -2347,6 +2350,9 @@ 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");
 
         if (rnp->gpnum != rnp->completed) {
 
@@ -2355,6 +2361,10 @@ 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,
+                                            "Startedleaf");
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
         } else {
@@ -2366,6 +2376,11 @@ 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,
+                                                    c, rnp->level,
+                                                    rnp->grplo, rnp->grphi,
+                                                    "Startedleafroot");
                         raw_spin_unlock(&rnp_root->lock); /* irqs disabled. */
                 } else {
 
@@ -2381,6 +2396,11 @@ 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,
+                                                    c, rnp->level,
+                                                    rnp->grplo, rnp->grphi,
+                                                    "Startedroot");
                         local_save_flags(flags1);
                         rcu_start_gp(rdp->rsp, flags1); /* Rlses ->lock. */
                 }
@@ -2396,6 +2416,9 @@ 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");
         for (;;) {
                 wait_event_interruptible(
                         rnp->nocb_gp_wq[c & 0x1],
@@ -2403,7 +2426,14 @@ 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,
+                                            rnp->gpnum, rnp->completed, c,
+                                            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");
         smp_mb(); /* Ensure that CB invocation happens after GP end. */
 }