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, 42 insertions, 3 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 4e24399cabc..7e0282949f8 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -166,6 +166,8 @@ void rcu_sched_qs(int cpu)
 
 	rdp->passed_quiesc_completed = rdp->gpnum - 1;
 	barrier();
+	if (rdp->passed_quiesc == 0)
+		trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
 	rdp->passed_quiesc = 1;
 }
 
@@ -175,6 +177,8 @@ void rcu_bh_qs(int cpu)
 
 	rdp->passed_quiesc_completed = rdp->gpnum - 1;
 	barrier();
+	if (rdp->passed_quiesc == 0)
+		trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
 	rdp->passed_quiesc = 1;
 }
 
@@ -319,6 +323,7 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
 	 * trust its state not to change because interrupts are disabled.
 	 */
 	if (cpu_is_offline(rdp->cpu)) {
+		trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl");
 		rdp->offline_fqs++;
 		return 1;
 	}
@@ -359,6 +364,7 @@ void rcu_enter_nohz(void)
 		local_irq_restore(flags);
 		return;
 	}
+	trace_rcu_dyntick("Start");
 	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
 	smp_mb__before_atomic_inc();  /* See above. */
 	atomic_inc(&rdtp->dynticks);
@@ -396,6 +402,7 @@ void rcu_exit_nohz(void)
 	/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
 	smp_mb__after_atomic_inc();  /* See above. */
 	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+	trace_rcu_dyntick("End");
 	local_irq_restore(flags);
 }
 
@@ -501,6 +508,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 	 * of the current RCU grace period.
 	 */
 	if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) {
+		trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti");
 		rdp->dynticks_fqs++;
 		return 1;
 	}
@@ -683,6 +691,7 @@ static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct
 		 * go looking for one.
 		 */
 		rdp->gpnum = rnp->gpnum;
+		trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
 		if (rnp->qsmask & rdp->grpmask) {
 			rdp->qs_pending = 1;
 			rdp->passed_quiesc = 0;
@@ -746,6 +755,7 @@ __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat
 
 		/* Remember that we saw this grace-period completion. */
 		rdp->completed = rnp->completed;
+		trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
 
 		/*
 		 * If we were in an extended quiescent state, we may have
@@ -856,6 +866,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
 
 	/* Advance to a new grace period and initialize state. */
 	rsp->gpnum++;
+	trace_rcu_grace_period(rsp->name, rsp->gpnum, "start");
 	WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
 	rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
 	rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
@@ -870,6 +881,9 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
 		rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
 		rcu_start_gp_per_cpu(rsp, rnp, rdp);
 		rcu_preempt_boost_start_gp(rnp);
+		trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
+					    rnp->level, rnp->grplo,
+					    rnp->grphi, rnp->qsmask);
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
 		return;
 	}
@@ -906,6 +920,9 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
 		if (rnp == rdp->mynode)
 			rcu_start_gp_per_cpu(rsp, rnp, rdp);
 		rcu_preempt_boost_start_gp(rnp);
+		trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
+					    rnp->level, rnp->grplo,
+					    rnp->grphi, rnp->qsmask);
 		raw_spin_unlock(&rnp->lock);	/* irqs remain disabled. */
 	}
 
@@ -939,6 +956,7 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
 	if (gp_duration > rsp->gp_max)
 		rsp->gp_max = gp_duration;
 	rsp->completed = rsp->gpnum;
+	trace_rcu_grace_period(rsp->name, rsp->completed, "end");
 	rsp->signaled = RCU_GP_IDLE;
 	rcu_start_gp(rsp, flags);  /* releases root node's rnp->lock. */
 }
@@ -967,6 +985,10 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
 			return;
 		}
 		rnp->qsmask &= ~mask;
+		trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
+						 mask, rnp->qsmask, rnp->level,
+						 rnp->grplo, rnp->grphi,
+						 !!rnp->gp_tasks);
 		if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
 
 			/* Other bits still set at this level, so done. */
@@ -1135,11 +1157,20 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
 		if (rnp->qsmaskinit != 0) {
 			if (rnp != rdp->mynode)
 				raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+			else
+				trace_rcu_grace_period(rsp->name,
+						       rnp->gpnum + 1 -
+						       !!(rnp->qsmask & mask),
+						       "cpuofl");
 			break;
 		}
-		if (rnp == rdp->mynode)
+		if (rnp == rdp->mynode) {
+			trace_rcu_grace_period(rsp->name,
+					       rnp->gpnum + 1 -
+					       !!(rnp->qsmask & mask),
+					       "cpuofl");
 			need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
-		else
+		} else
 			raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
 		mask = rnp->grpmask;
 		rnp = rnp->parent;
@@ -1226,7 +1257,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
 		next = list->next;
 		prefetch(next);
 		debug_rcu_head_unqueue(list);
-		__rcu_reclaim(list);
+		__rcu_reclaim(rsp->name, list);
 		list = next;
 		if (++count >= bl)
 			break;
@@ -1552,6 +1583,12 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
 	rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
 	rdp->qlen++;
 
+	if (__is_kfree_rcu_offset((unsigned long)func))
+		trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
+					 rdp->qlen);
+	else
+		trace_rcu_callback(rsp->name, head, rdp->qlen);
+
 	/* If interrupts were disabled, don't dive into RCU core. */
 	if (irqs_disabled_flags(flags)) {
 		local_irq_restore(flags);
@@ -1850,6 +1887,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
 	rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
 #endif /* #ifdef CONFIG_NO_HZ */
 	rdp->cpu = cpu;
+	rdp->rsp = rsp;
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }
 
@@ -1898,6 +1936,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
 			rdp->gpnum = rnp->completed; /* if GP in progress... */
 			rdp->completed = rnp->completed;
 			rdp->passed_quiesc_completed = rnp->completed - 1;
+			trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
 		}
 		raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
 		rnp = rnp->parent;