rcu: Deconfuse dynticks entry-exit tracing

The trace_rcu_dyntick() trace event did not print both the old and
the new value of the nesting level, and furthermore printed only
the low-order 32 bits of it.  This could result in some confusion
when interpreting trace-event dumps, so this commit prints both
the old and the new value, prints the full 64 bits, and also selects
the process-entry/exit increment to print nicely in hexadecimal.

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

1 files changed, 17 insertions, 11 deletions

diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index b4e0b4981768..9b9bdf666fb5 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -53,20 +53,21 @@ static void __call_rcu(struct rcu_head *head,
 
 #include "rcutiny_plugin.h"
 
-static long long rcu_dynticks_nesting = LLONG_MAX / 2;
+static long long rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
 
 /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
-static void rcu_idle_enter_common(void)
+static void rcu_idle_enter_common(long long oldval)
 {
         if (rcu_dynticks_nesting) {
-                RCU_TRACE(trace_rcu_dyntick("--=", rcu_dynticks_nesting));
+                RCU_TRACE(trace_rcu_dyntick("--=",
+                                            oldval, rcu_dynticks_nesting));
                 return;
         }
-        RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting));
+        RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
         if (!idle_cpu(smp_processor_id())) {
                 WARN_ON_ONCE(1);        /* must be idle task! */
                 RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
-                                            rcu_dynticks_nesting));
+                                            oldval, rcu_dynticks_nesting));
                 ftrace_dump(DUMP_ALL);
         }
         rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
@@ -79,10 +80,12 @@ static void rcu_idle_enter_common(void)
 void rcu_idle_enter(void)
 {
         unsigned long flags;
+        long long oldval;
 
         local_irq_save(flags);
+        oldval = rcu_dynticks_nesting;
         rcu_dynticks_nesting = 0;
-        rcu_idle_enter_common();
+        rcu_idle_enter_common(oldval);
         local_irq_restore(flags);
 }
 
@@ -92,11 +95,13 @@ void rcu_idle_enter(void)
 void rcu_irq_exit(void)
 {
         unsigned long flags;
+        long long oldval;
 
         local_irq_save(flags);
+        oldval = rcu_dynticks_nesting;
         rcu_dynticks_nesting--;
         WARN_ON_ONCE(rcu_dynticks_nesting < 0);
-        rcu_idle_enter_common();
+        rcu_idle_enter_common(oldval);
         local_irq_restore(flags);
 }
 
@@ -104,14 +109,15 @@ void rcu_irq_exit(void)
 static void rcu_idle_exit_common(long long oldval)
 {
         if (oldval) {
-                RCU_TRACE(trace_rcu_dyntick("++=", rcu_dynticks_nesting));
+                RCU_TRACE(trace_rcu_dyntick("++=",
+                                            oldval, rcu_dynticks_nesting));
                 return;
         }
-        RCU_TRACE(trace_rcu_dyntick("End", oldval));
+        RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
         if (!idle_cpu(smp_processor_id())) {
                 WARN_ON_ONCE(1);        /* must be idle task! */
                 RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
-                          oldval));
+                          oldval, rcu_dynticks_nesting));
                 ftrace_dump(DUMP_ALL);
         }
 }
@@ -127,7 +133,7 @@ void rcu_idle_exit(void)
         local_irq_save(flags);
         oldval = rcu_dynticks_nesting;
         WARN_ON_ONCE(oldval != 0);
-        rcu_dynticks_nesting = LLONG_MAX / 2;
+        rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
         rcu_idle_exit_common(oldval);
         local_irq_restore(flags);
 }