linux-kernel - [RFC][PATCH 2/4] sched: Have sched_class

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Message-Id: <20191219214558.682913590@goodmis.org>
Date:   Thu, 19 Dec 2019 16:44:53 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kirill Tkhai <tkhai@...dex.ru>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "juri.lelli@...hat.com" <juri.lelli@...hat.com>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "dietmar.eggemann@....com" <dietmar.eggemann@....com>,
        "bsegall@...gle.com" <bsegall@...gle.com>,
        "mgorman@...e.de" <mgorman@...e.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [RFC][PATCH 2/4] sched: Have sched_class_highest define by vmlinux.lds.h

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

Now that the sched_class descriptors are defined by the linker script, and
this needs to be aware of the existance of stop_sched_class when SMP is
enabled or not, as it is used as the "highest" priority when defined. Move
the declaration of sched_class_highest to the same location in the linker
script that inserts stop_sched_class, and this will also make it easier to
see what should be defined as the highest class, as this linker script
location defines the priorities as well.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 include/asm-generic/vmlinux.lds.h | 11 ++++++++++-
 kernel/sched/sched.h              |  9 +++------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 772d961c69a5..1c14c4ddf785 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -109,9 +109,16 @@
 #endif
 
 #ifdef CONFIG_SMP
-#define STOP_SCHED_CLASS	*(__stop_sched_class)
+#define STOP_SCHED_CLASS		\
+	STRUCT_ALIGN();			\
+	sched_class_highest = .;	\
+	*(__stop_sched_class)
+#define BEFORE_DL_SCHED_CLASS
 #else
 #define STOP_SCHED_CLASS
+#define BEFORE_DL_SCHED_CLASS		\
+	STRUCT_ALIGN();			\
+	sched_class_highest = .;
 #endif
 
 /*
@@ -120,9 +127,11 @@
  * relation to each other.
  */
 #define SCHED_DATA				\
+	STRUCT_ALIGN();				\
 	*(__idle_sched_class)			\
 	*(__fair_sched_class)			\
 	*(__rt_sched_class)			\
+	BEFORE_DL_SCHED_CLASS			\
 	*(__dl_sched_class)			\
 	STOP_SCHED_CLASS
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 280a3c735935..0554c588ad85 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1771,17 +1771,14 @@ static inline void set_next_task(struct rq *rq, struct task_struct *next)
 	next->sched_class->set_next_task(rq, next, false);
 }
 
-#ifdef CONFIG_SMP
-#define sched_class_highest (&stop_sched_class)
-#else
-#define sched_class_highest (&dl_sched_class)
-#endif
+/* Defined in include/asm-generic/vmlinux.lds.h */
+extern struct sched_class sched_class_highest;
 
 #define for_class_range(class, _from, _to) \
 	for (class = (_from); class != (_to); class = class->next)
 
 #define for_each_class(class) \
-	for_class_range(class, sched_class_highest, NULL)
+	for_class_range(class, &sched_class_highest, NULL)
 
 extern const struct sched_class stop_sched_class;
 extern const struct sched_class dl_sched_class;
-- 
2.24.0