Commit-ID: bd2b879a1ca55486fdb9dcac691bfd3dd79c83d6
Gitweb: https://git.kernel.org/tip/bd2b879a1ca55486fdb9dcac691bfd3dd79c83d6
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 4 Oct 2017 12:29:01 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 28 Nov 2017 15:51:18 -0800
rcu: Add tracing to irq/NMI dyntick-idle transitions
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
include/trace/events/rcu.h | 14 ++++++++------
kernel/rcu/tree.c | 6 ++++++
2 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 59d40c4..4674b21 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -421,16 +421,18 @@ TRACE_EVENT(rcu_fqs,
/*
* Tracepoint for dyntick-idle entry/exit events. These take a string
- * as argument: "Start" for entering dyntick-idle mode, "End" for
- * leaving it, "--=" for events moving towards idle, and "++=" for events
- * moving away from idle. "Error on entry: not idle task" and "Error on
- * exit: not idle task" indicate that a non-idle task is erroneously
+ * as argument: "Start" for entering dyntick-idle mode, "Startirq" for
+ * entering it from irq/NMI, "End" for leaving it, "Endirq" for leaving it
+ * to irq/NMI, "--=" for events moving towards idle, and "++=" for events
+ * moving away from idle. "Error on entry: not idle task" and "Error
+ * on exit: not idle task" indicate that a non-idle task is erroneously
* toying with the idle loop.
*
* These events also take a pair of numbers, which indicate the nesting
* depth before and after the event of interest. Note that task-related
- * events use the upper bits of each number, while interrupt-related
- * events use the lower bits.
+ * and interrupt-related events use two separate counters, and that the
+ * "++=" and "--=" events for irq/NMI will change the counter by two,
+ * otherwise by one.
*/
TRACE_EVENT(rcu_dyntick,
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 444aa2b..d069ba2 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -880,12 +880,15 @@ void rcu_nmi_exit(void)
* leave it in non-RCU-idle state.
*/
if (rdtp->dynticks_nmi_nesting != 1) {
+ trace_rcu_dyntick(TPS("--="), rdtp->dynticks_nmi_nesting,
+ rdtp->dynticks_nmi_nesting - 2);
WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* No store tearing. */
rdtp->dynticks_nmi_nesting - 2);
return;
}
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
+ trace_rcu_dyntick(TPS("Startirq"), rdtp->dynticks_nmi_nesting, 0);
WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
rcu_dynticks_eqs_enter();
}
@@ -1057,6 +1060,9 @@ void rcu_nmi_enter(void)
rcu_dynticks_eqs_exit();
incby = 1;
}
+ trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
+ rdtp->dynticks_nmi_nesting,
+ rdtp->dynticks_nmi_nesting + incby);
WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* Prevent store tearing. */
rdtp->dynticks_nmi_nesting + incby);
barrier();
--
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