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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@elte.hu>,
	Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Andrew Theurer <habanero@linux.vnet.ibm.com>
Subject: [PATCH 2/2] sched: Check if lowest_mask is initialized in find_lowest_rq
Date: Tue, 14 Jun 2011 18:36:25 -0400
Message-ID: <20110614223657.824872966@goodmis.org> (raw)
In-Reply-To: <20110614223623.876681637@goodmis.org>


[-- Attachment #0: 0002-sched-Check-if-lowest_mask-is-initialized-in-find_lo.patch --]
[-- Type: text/plain, Size: 1269 bytes --]

From: Steven Rostedt <rostedt@goodmis.org>

On system boot up, the lowest_mask is initialized with early_initcall.
But RT tasks may wake up on other early_initcall callers before the
lowest_mask is initialized, causing a system crash.

The commit d72bce0e67 rcu: Cure load woes
was the first commit to wake up RT tasks in early init. Before this
commit this bug should not happen.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Reported-by: Andrew Theurer <habanero@linux.vnet.ibm.com>
Tested-by: Andrew Theurer <habanero@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1308014683.9218.107.camel@gandalf.stny.rr.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/sched_rt.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 9b8d5dc..10d0182 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1239,6 +1239,10 @@ static int find_lowest_rq(struct task_struct *task)
 	int this_cpu = smp_processor_id();
 	int cpu      = task_cpu(task);
 
+	/* Make sure the mask is initialized first */
+	if (unlikely(!lowest_mask))
+		return -1;
+
 	if (task->rt.nr_cpus_allowed == 1)
 		return -1; /* No other targets possible */
 
-- 
1.7.4.4



  parent reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-14 22:36 [PATCH 0/2] [GIT PULL][v3.0] sched: various fixes Steven Rostedt
2011-06-14 22:36 ` [PATCH 1/2] sched: Fix need_resched() when checking peempt Steven Rostedt
2011-06-15  9:50   ` [tip:sched/urgent] " tip-bot for Hillf Danton
2011-06-14 22:36 ` Steven Rostedt [this message]
2011-06-15  0:40   ` [PATCH 2/2] sched: Check if lowest_mask is initialized in find_lowest_rq Paul E. McKenney
2011-06-15  8:17   ` Peter Zijlstra
2011-06-15  9:50   ` [tip:sched/urgent] sched: Check if lowest_mask is initialized in find_lowest_rq() tip-bot for Steven Rostedt

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