From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon, 11 Jul 2011 14:28:50 +0000 (+0200)
Subject: sched: Fix 32bit race
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=c64be78ffb415278d7d32d6f55de95c73dcc19a4;p=~shefty%2Frdma-dev.git

sched: Fix 32bit race

Commit 3fe1698b7fe0 ("sched: Deal with non-atomic min_vruntime reads
on 32bit") forgot to initialize min_vruntime_copy which could lead to
an infinite while loop in task_waking_fair() under some circumstances
(early boot, lucky timing).

[ This bug was also reported by others that blamed it on the RCU
  initialization problems ]

Reported-and-tested-by: Bruno Wolff III <bruno@wolff.to>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/sched.c b/kernel/sched.c
index 9769c756ad6..3dc716f6d8a 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7757,6 +7757,9 @@ static void init_cfs_rq(struct cfs_rq *cfs_rq, struct rq *rq)
 #endif
 #endif
 	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
+#ifndef CONFIG_64BIT
+	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
+#endif
 }
 
 static void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)