linux-kernel - [08/82] sched: Drop all load weight manipulation for RT tasks

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Message-Id: <20101119215639.401285027@clark.site>
Date:	Fri, 19 Nov 2010 13:55:29 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Lennart Poettering <lennart@...ttering.net>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>
Subject: [08/82] sched: Drop all load weight manipulation for RT tasks

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Linus Walleij <linus.walleij@...ricsson.com>

commit 17bdcf949d03306b308c5fb694849cd35f119807 upstream.

Load weights are for the CFS, they do not belong in the RT task. This makes all
RT scheduling classes leave the CFS weights alone.

This fixes a real bug as well: I noticed the following phonomena: a process
elevated to SCHED_RR forks with SCHED_RESET_ON_FORK set, and the child is
indeed SCHED_OTHER, and the niceval is indeed reset to 0. However the weight
inserted by set_load_weight() remains at 0, giving the task insignificat
priority.

With this fix, the weight is reset to what the task had before being elevated
to SCHED_RR/SCHED_FIFO.

Cc: Lennart Poettering <lennart@...ttering.net>
Signed-off-by: Linus Walleij <linus.walleij@...ricsson.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <1286807811-10568-1-git-send-email-linus.walleij@...ricsson.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/sched.c |    6 ------
 1 file changed, 6 deletions(-)

--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1830,12 +1830,6 @@ static void dec_nr_running(struct rq *rq
 
 static void set_load_weight(struct task_struct *p)
 {
-	if (task_has_rt_policy(p)) {
-		p->se.load.weight = 0;
-		p->se.load.inv_weight = WMULT_CONST;
-		return;
-	}
-
 	/*
 	 * SCHED_IDLE tasks get minimal weight:
 	 */


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