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Subject[PATCH 24/24] nohz: Add some tracing
Date
Not for merge, just for debugging.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/tick-sched.c | 27 ++++++++++++++++++++++-----
1 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4f4fa13..f75a85f 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -142,6 +142,7 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
ts->idle_jiffies++;
}
#endif
+ trace_printk("tick\n");
update_process_times(user_mode(regs));
profile_tick(CPU_PROFILING);
}
@@ -589,17 +590,30 @@ void tick_nohz_idle_enter(void)
#ifdef CONFIG_NO_HZ_FULL
static bool can_stop_full_tick(int cpu)
{
- if (!sched_can_stop_tick())
+ if (!sched_can_stop_tick()) {
+ trace_printk("Can't stop: sched\n");
return false;
+ }

- if (!rcu_is_nocb_cpu(cpu))
+ if (!rcu_is_nocb_cpu(cpu)) {
+ trace_printk("Can't stop: not RCU nocb\n");
return false;
+ }

- if (rcu_pending(cpu))
+ /*
+ * Keep the tick if we are asked to report a quiescent state.
+ * This must be further optimized (avoid checks for local callbacks,
+ * ignore RCU in userspace, etc...
+ */
+ if (rcu_pending(cpu)) {
+ trace_printk("Can't stop: RCU pending\n");
return false;
+ }

- if (posix_cpu_timers_running(current))
+ if (posix_cpu_timers_running(current)) {
+ trace_printk("Can't stop: posix CPU timers running\n");
return false;
+ }

return true;
}
@@ -613,12 +627,15 @@ static void tick_nohz_full_stop_tick(struct tick_sched *ts)
if (!tick_nohz_full_cpu(cpu) || is_idle_task(current))
return;

- if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
+ if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) {
+ trace_printk("Can't stop: NOHZ_MODE_INACTIVE\n");
return;
+ }

if (!can_stop_full_tick(cpu))
return;

+ trace_printk("Stop tick\n");
tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
#endif
}
--
1.7.5.4


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