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* [PATCH v2] sched,tracing: Correct trace_sched_pi_setprio() for deboosting
  2018-05-24  8:37     ` Peter Zijlstra
@ 2018-05-24 13:26       ` " Sebastian Andrzej Siewior
  0 siblings, 0 replies; 1+ messages in thread
From: Sebastian Andrzej Siewior @ 2018-05-24 13:26 UTC (permalink / raw)
  To: Peter Zijlstra; +Cc: linux-kernel, Steven Rostedt, Ingo Molnar, Thomas Gleixner

Since commit b91473ff6e97 ("sched,tracing: Update
trace_sched_pi_setprio()") the sched_pi_setprio trace point shows the
"newprio" during a deboost:
|futex sched_pi_setprio: comm=futex_requeue_p pid=2234 oldprio=98 newprio=98
|futex sched_switch: prev_comm=futex_requeue_p prev_pid=2234 prev_prio=120

This patch open codes __rt_effective_prio() in the tracepoint as the
`newprio' to get the old behaviour back / the correct priority:

|futex sched_pi_setprio: comm=futex_requeue_p pid=2220 oldprio=98 newprio=120
|futex sched_switch: prev_comm=futex_requeue_p prev_pid=2220 prev_prio=120

Peter suggested to open code the new priority so people using tracehook
could get the deadline data out.

Reported-by: Mansky Christian <man@keba.com>
Fixes: b91473ff6e97 ("sched,tracing: Update trace_sched_pi_setprio()")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
v1…v2: Open code __rt_effective_prio() in sched_pi_setprio macro as
suggested by PeterZ.

 include/trace/events/sched.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index bc01e06bc716..0be866c91f62 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -435,7 +435,9 @@ TRACE_EVENT(sched_pi_setprio,
 		memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN);
 		__entry->pid		= tsk->pid;
 		__entry->oldprio	= tsk->prio;
-		__entry->newprio	= pi_task ? pi_task->prio : tsk->prio;
+		__entry->newprio	= pi_task ?
+				min(tsk->normal_prio, pi_task->prio) :
+				tsk->normal_prio;
 		/* XXX SCHED_DEADLINE bits missing */
 	),
 
-- 
2.17.0

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2018-05-23 14:11 [PATCH] sched,tracing: Correct trace_sched_pi_setprio() for deboosting Sebastian Andrzej Siewior
2018-05-23 17:28 ` Peter Zijlstra
2018-05-24  7:44   ` Sebastian Andrzej Siewior
2018-05-24  8:37     ` Peter Zijlstra
2018-05-24 13:26       ` [PATCH v2] " Sebastian Andrzej Siewior

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