linux-kernel - [PATCH v4 1/3] sched: Add WF_TTWU, WF

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Date:   Mon,  2 Nov 2020 18:45:12 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: [PATCH v4 1/3] sched: Add WF_TTWU, WF_EXEC wakeup flags

To remove the sd_flag parameter of select_task_rq(), we need another way of
encoding wakeup types. There already is a WF_FORK flag, add the missing two.

With that said, we still need an easy way to turn WF_foo into
SD_bar (e.g. WF_TTWU into SD_BALANCE_WAKE). As suggested by Peter, let's
make our lives easier and make them match exactly, and throw in some
compile-time checks for good measure.

Signed-off-by: Valentin Schneider <valentin.schneider@....com>
---
 kernel/sched/sched.h | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index df80bfcea92e..65666c52f347 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1714,13 +1714,20 @@ static inline int task_on_rq_migrating(struct task_struct *p)
 	return READ_ONCE(p->on_rq) == TASK_ON_RQ_MIGRATING;
 }
 
-/*
- * wake flags
- */
-#define WF_SYNC			0x01		/* Waker goes to sleep after wakeup */
-#define WF_FORK			0x02		/* Child wakeup after fork */
-#define WF_MIGRATED		0x04		/* Internal use, task got migrated */
-#define WF_ON_CPU		0x08		/* Wakee is on_cpu */
+/* Wake flags. The first three directly map to some SD flag value */
+#define WF_EXEC     0x02 /* Wakeup after exec; maps to SD_BALANCE_EXEC */
+#define WF_FORK     0x04 /* Wakeup after fork; maps to SD_BALANCE_FORK */
+#define WF_TTWU     0x08 /* Wakeup;            maps to SD_BALANCE_WAKE */
+
+#define WF_SYNC     0x10 /* Waker goes to sleep after wakeup */
+#define WF_MIGRATED 0x20 /* Internal use, task got migrated */
+#define WF_ON_CPU   0x40 /* Wakee is on_cpu */
+
+#ifdef CONFIG_SMP
+static_assert(WF_EXEC == SD_BALANCE_EXEC);
+static_assert(WF_FORK == SD_BALANCE_FORK);
+static_assert(WF_TTWU == SD_BALANCE_WAKE);
+#endif
 
 /*
  * To aid in avoiding the subversion of "niceness" due to uneven distribution
-- 
2.27.0