linux-kernel - [PATCH RT 6/8] sched: migrate_enable: Set state to TASK

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Date:   Sat, 27 Jul 2019 00:56:36 -0500
From:   Scott Wood <swood@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Scott Wood <swood@...hat.com>
Subject: [PATCH RT 6/8] sched: migrate_enable: Set state to TASK_RUNNING

If migrate_enable() is called while a task is preparing to sleep
(state != TASK_RUNNING), that triggers a debug check in stop_one_cpu().
Explicitly reset state to acknowledge that we're accepting the spurious
wakeup.

Signed-off-by: Scott Wood <swood@...hat.com>
---
 kernel/sched/core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 38a9a9df5638..eb27a9bf70d7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7396,6 +7396,14 @@ void migrate_enable(void)
 			unpin_current_cpu();
 			preempt_lazy_enable();
 			preempt_enable();
+
+			/*
+			 * Avoid sleeping with an existing non-running
+			 * state.  This will result in a spurious wakeup
+			 * for the calling context.
+			 */
+			__set_current_state(TASK_RUNNING);
+
 			sleeping_lock_inc();
 			stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
 			sleeping_lock_dec();
-- 
1.8.3.1