linux-kernel - [PATCH] sched: make pushable_tasks CONFIG

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Message-ID: <1291143093.2697.298.camel@Palantir>
Date:	Tue, 30 Nov 2010 19:51:33 +0100
From:	Dario Faggioli <raistlin@...ux.it>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gregory Haskins <ghaskins@...ell.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>
Subject: [PATCH] sched: make pushable_tasks CONFIG_SMP dependant.

As noted by Peter Zijlstra here https://lkml.org/lkml/2010/11/10/391
(while reviewing other stuff, though), tracking pushable tasks
only makes sense on SMPs.

Signed-off-by: Dario Faggioli <raistlin@...ux.it>
---
 include/linux/init_task.h |    9 ++++++++-
 include/linux/sched.h     |    2 ++
 kernel/sched.c            |    2 ++
 3 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 1f8c06c..6ed8812 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -12,6 +12,13 @@
 #include <linux/securebits.h>
 #include <net/net_namespace.h>
 
+#ifdef CONFIG_SMP
+# define INIT_PUSHABLE_TASKS(tsk)					\
+	.pushable_tasks = PLIST_NODE_INIT(tsk.pushable_tasks, MAX_PRIO),
+#else
+# define INIT_PUSHABLE_TASKS(tsk)
+#endif
+
 extern struct files_struct init_files;
 extern struct fs_struct init_fs;
 
@@ -137,7 +144,7 @@ extern struct cred init_cred;
 		.nr_cpus_allowed = NR_CPUS,				\
 	},								\
 	.tasks		= LIST_HEAD_INIT(tsk.tasks),			\
-	.pushable_tasks = PLIST_NODE_INIT(tsk.pushable_tasks, MAX_PRIO), \
+	INIT_PUSHABLE_TASKS(tsk)					\
 	.ptraced	= LIST_HEAD_INIT(tsk.ptraced),			\
 	.ptrace_entry	= LIST_HEAD_INIT(tsk.ptrace_entry),		\
 	.real_parent	= &tsk,						\
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b0fc8ee..eae4131 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1244,7 +1244,9 @@ struct task_struct {
 #endif
 
 	struct list_head tasks;
+#ifdef CONFIG_SMP
 	struct plist_node pushable_tasks;
+#endif
 
 	struct mm_struct *mm, *active_mm;
 #if defined(SPLIT_RSS_COUNTING)
diff --git a/kernel/sched.c b/kernel/sched.c
index 0debad9..166f9f8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2595,7 +2595,9 @@ void sched_fork(struct task_struct *p, int clone_flags)
 	/* Want to start with kernel preemption disabled. */
 	task_thread_info(p)->preempt_count = 1;
 #endif
+#ifdef CONFIG_SMP
 	plist_node_init(&p->pushable_tasks, MAX_PRIO);
+#endif
 
 	put_cpu();
 }
-- 
1.7.2.3

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://retis.sssup.it/people/faggioli -- dario.faggioli@...ber.org

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