Thread (24 messages) 24 messages, 2 authors, 2018-10-02
STALE2805d

[PATCH RT 08/22] sched, tracing: Fix trace_sched_pi_setprio() for deboosting

From: Julia Cartwright <hidden>
Date: 2018-08-06 09:18:36
Also in: lkml
Subsystem: the rest, tracing · Maintainers: Linus Torvalds, Steven Rostedt, Masami Hiramatsu

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

4.9.115-rt94-rc1 stable review patch.
If you have any objection to the inclusion of this patch, let me know.
--- 8< --- 8< --- 8< ---
[ Upstream commit 4ff648decf4712d39f184fc2df3163f43975575a ]

Since the following 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"34 oldprio˜ newprio=98
  |futex sched_switch: prev_comm=futex_requeue_p prev_pid"34 prev_prio0

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"20 oldprio˜ newprio=120
  |futex sched_switch: prev_comm=futex_requeue_p prev_pid"20 prev_prio0

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

Reported-by: Mansky Christian <redacted>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <redacted>
Fixes: b91473ff6e97 ("sched,tracing: Update trace_sched_pi_setprio()")
Link: http://lkml.kernel.org/r/20180524132647.gg6ziuogczdmjjzu@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Julia Cartwright <redacted>
---
 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 516ae88cddf4..742682079acf 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -429,7 +429,9 @@ 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 */
 	),
 
-- 
2.18.0
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