rcu: Add grace-period, quiescent-state, and call_rcu trace events

Add trace events to record grace-period start and end, quiescent states,
CPUs noticing grace-period start and end, grace-period initialization,
call_rcu() invocation, tasks blocking in RCU read-side critical sections,
tasks exiting those same critical sections, force_quiescent_state()
detection of dyntick-idle and offline CPUs, CPUs entering and leaving
dyntick-idle mode (except from NMIs), CPUs coming online and going
offline, and CPUs being kicked for staying in dyntick-idle mode for too
long (as in many weeks, even on 32-bit systems).

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

rcu: Add the rcu flavor to callback trace events

The earlier trace events for registering RCU callbacks and for invoking
them did not include the RCU flavor (rcu_bh, rcu_preempt, or rcu_sched).
This commit adds the RCU flavor to those trace events.

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

1 files changed, 19 insertions, 3 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 94d9ca1e4061..bdb2e82f78d3 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -124,6 +124,8 @@ static void rcu_preempt_qs(int cpu)
 
         rdp->passed_quiesc_completed = rdp->gpnum - 1;
         barrier();
+        if (rdp->passed_quiesc == 0)
+                trace_rcu_grace_period("rcu_preempt", rdp->gpnum, "cpuqs");
         rdp->passed_quiesc = 1;
         current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
 }
@@ -190,6 +192,11 @@ static void rcu_preempt_note_context_switch(int cpu)
                         if (rnp->qsmask & rdp->grpmask)
                                 rnp->gp_tasks = &t->rcu_node_entry;
                 }
+                trace_rcu_preempt_task(rdp->rsp->name,
+                                       t->pid,
+                                       (rnp->qsmask & rdp->grpmask)
+                                       ? rnp->gpnum
+                                       : rnp->gpnum + 1);
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
         } else if (t->rcu_read_lock_nesting < 0 &&
                    t->rcu_read_unlock_special) {
@@ -344,6 +351,8 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
                 smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
                 np = rcu_next_node_entry(t, rnp);
                 list_del_init(&t->rcu_node_entry);
+                trace_rcu_unlock_preempted_task("rcu_preempt",
+                                                rnp->gpnum, t->pid);
                 if (&t->rcu_node_entry == rnp->gp_tasks)
                         rnp->gp_tasks = np;
                 if (&t->rcu_node_entry == rnp->exp_tasks)
@@ -364,10 +373,17 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
                  * we aren't waiting on any CPUs, report the quiescent state.
                  * Note that rcu_report_unblock_qs_rnp() releases rnp->lock.
                  */
-                if (empty)
-                        raw_spin_unlock_irqrestore(&rnp->lock, flags);
-                else
+                if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) {
+                        trace_rcu_quiescent_state_report("preempt_rcu",
+                                                         rnp->gpnum,
+                                                         0, rnp->qsmask,
+                                                         rnp->level,
+                                                         rnp->grplo,
+                                                         rnp->grphi,
+                                                         !!rnp->gp_tasks);
                         rcu_report_unblock_qs_rnp(rnp, flags);
+                } else
+                        raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
 #ifdef CONFIG_RCU_BOOST
                 /* Unboost if we were boosted. */