linux-kernel - [tip:sched/core] sched: fix broken SCHED_RESET_ON

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Date:	Sun, 14 Aug 2011 15:58:42 GMT
From:	tip-bot for Mike Galbraith <efault@....de>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, efault@....de, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:sched/core] sched: fix broken SCHED_RESET_ON_FORK handling

Commit-ID:  c350a04efd1c89cd256b2abc8f07a21d0d53ff24
Gitweb:     http://git.kernel.org/tip/c350a04efd1c89cd256b2abc8f07a21d0d53ff24
Author:     Mike Galbraith <efault@....de>
AuthorDate: Wed, 27 Jul 2011 17:14:55 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Sun, 14 Aug 2011 12:00:43 +0200

sched: fix broken SCHED_RESET_ON_FORK handling

Setting child->prio = current->normal_prio _after_ SCHED_RESET_ON_FORK has
been handled for an RT parent gives birth to a deranged mutant child with
non-RT policy, but RT prio and sched_class.

Move PI leakage protection up, always set priorities and weight, and if the
child is leaving RT class, reset rt_priority to the proper value.

Signed-off-by: Mike Galbraith <efault@....de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1311779695.8691.2.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched.c |   25 ++++++++++++-------------
 1 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index b1e8f0e..cf427bb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2844,19 +2844,23 @@ void sched_fork(struct task_struct *p)
 	p->state = TASK_RUNNING;
 
 	/*
+	 * Make sure we do not leak PI boosting priority to the child.
+	 */
+	p->prio = current->normal_prio;
+
+	/*
 	 * Revert to default priority/policy on fork if requested.
 	 */
 	if (unlikely(p->sched_reset_on_fork)) {
-		if (p->policy == SCHED_FIFO || p->policy == SCHED_RR) {
+		if (task_has_rt_policy(p)) {
 			p->policy = SCHED_NORMAL;
-			p->normal_prio = p->static_prio;
-		}
-
-		if (PRIO_TO_NICE(p->static_prio) < 0) {
 			p->static_prio = NICE_TO_PRIO(0);
-			p->normal_prio = p->static_prio;
-			set_load_weight(p);
-		}
+			p->rt_priority = 0;
+		} else if (PRIO_TO_NICE(p->static_prio) < 0)
+			p->static_prio = NICE_TO_PRIO(0);
+
+		p->prio = p->normal_prio = __normal_prio(p);
+		set_load_weight(p);
 
 		/*
 		 * We don't need the reset flag anymore after the fork. It has
@@ -2865,11 +2869,6 @@ void sched_fork(struct task_struct *p)
 		p->sched_reset_on_fork = 0;
 	}
 
-	/*
-	 * Make sure we do not leak PI boosting priority to the child.
-	 */
-	p->prio = current->normal_prio;
-
 	if (!rt_prio(p->prio))
 		p->sched_class = &fair_sched_class;
 
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