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>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 489b62a..06e40dd 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -196,7 +196,7 @@
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
- .dynticks_nesting = LLONG_MAX / 2,
+ .dynticks_nesting = DYNTICK_TASK_NESTING,
.dynticks = ATOMIC_INIT(1),
};
@@ -348,17 +348,17 @@
* we really have entered idle, and must do the appropriate accounting.
* The caller must have disabled interrupts.
*/
-static void rcu_idle_enter_common(struct rcu_dynticks *rdtp)
+static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
{
if (rdtp->dynticks_nesting) {
- trace_rcu_dyntick("--=", rdtp->dynticks_nesting);
+ trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);
return;
}
- trace_rcu_dyntick("Start", rdtp->dynticks_nesting);
+ trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
if (!idle_cpu(smp_processor_id())) {
WARN_ON_ONCE(1); /* must be idle task! */
trace_rcu_dyntick("Error on entry: not idle task",
- rdtp->dynticks_nesting);
+ oldval, rdtp->dynticks_nesting);
ftrace_dump(DUMP_ALL);
}
/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
@@ -383,12 +383,14 @@
void rcu_idle_enter(void)
{
unsigned long flags;
+ long long oldval;
struct rcu_dynticks *rdtp;
local_irq_save(flags);
rdtp = &__get_cpu_var(rcu_dynticks);
+ oldval = rdtp->dynticks_nesting;
rdtp->dynticks_nesting = 0;
- rcu_idle_enter_common(rdtp);
+ rcu_idle_enter_common(rdtp, oldval);
local_irq_restore(flags);
}
@@ -411,13 +413,15 @@
void rcu_irq_exit(void)
{
unsigned long flags;
+ long long oldval;
struct rcu_dynticks *rdtp;
local_irq_save(flags);
rdtp = &__get_cpu_var(rcu_dynticks);
+ oldval = rdtp->dynticks_nesting;
rdtp->dynticks_nesting--;
WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
- rcu_idle_enter_common(rdtp);
+ rcu_idle_enter_common(rdtp, oldval);
local_irq_restore(flags);
}
@@ -431,7 +435,7 @@
static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
{
if (oldval) {
- trace_rcu_dyntick("++=", rdtp->dynticks_nesting);
+ trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting);
return;
}
smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
@@ -439,10 +443,11 @@
/* 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", oldval);
+ trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
if (!idle_cpu(smp_processor_id())) {
WARN_ON_ONCE(1); /* must be idle task! */
- trace_rcu_dyntick("Error on exit: not idle task", oldval);
+ trace_rcu_dyntick("Error on exit: not idle task",
+ oldval, rdtp->dynticks_nesting);
ftrace_dump(DUMP_ALL);
}
}
@@ -453,8 +458,8 @@
* Exit idle mode, in other words, -enter- the mode in which RCU
* read-side critical sections can occur.
*
- * We crowbar the ->dynticks_nesting field to LLONG_MAX/2 to allow for
- * the possibility of usermode upcalls messing up our count
+ * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NESTING to
+ * allow for the possibility of usermode upcalls messing up our count
* of interrupt nesting level during the busy period that is just
* now starting.
*/
@@ -468,7 +473,7 @@
rdtp = &__get_cpu_var(rcu_dynticks);
oldval = rdtp->dynticks_nesting;
WARN_ON_ONCE(oldval != 0);
- rdtp->dynticks_nesting = LLONG_MAX / 2;
+ rdtp->dynticks_nesting = DYNTICK_TASK_NESTING;
rcu_idle_exit_common(rdtp, oldval);
local_irq_restore(flags);
}
@@ -2012,7 +2017,7 @@
rdp->nxttail[i] = &rdp->nxtlist;
rdp->qlen = 0;
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
- WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);
+ WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_NESTING);
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
rdp->cpu = cpu;
rdp->rsp = rsp;
@@ -2040,7 +2045,7 @@
rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = rsp->n_force_qs;
rdp->blimit = blimit;
- WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);
+ WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_NESTING);
WARN_ON_ONCE((atomic_read(&rdp->dynticks->dynticks) & 0x1) != 1);
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */