Commit-ID: 3fe1698b7fe05aeb063564e71e40d09f28d8e80c
Gitweb: http://git.kernel.org/tip/3fe1698b7fe05aeb063564e71e40d09f28d8e80c
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Tue, 5 Apr 2011 17:23:48 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 14 Apr 2011 08:52:37 +0200
sched: Deal with non-atomic min_vruntime reads on 32bits
In order to avoid reading partial updated min_vruntime values on 32bit
implement a seqcount like solution.
Reviewed-by: Frank Rowand <frank.rowand@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20110405152729.111378493@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/sched.c | 3 +++
kernel/sched_fair.c | 19 +++++++++++++++++--
2 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 46f42ca..7a5eb26 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -312,6 +312,9 @@ struct cfs_rq {
u64 exec_clock;
u64 min_vruntime;
+#ifndef CONFIG_64BIT
+ u64 min_vruntime_copy;
+#endif
struct rb_root tasks_timeline;
struct rb_node *rb_leftmost;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ad4c414f..054cebb 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -358,6 +358,10 @@ static void update_min_vruntime(struct cfs_rq *cfs_rq)
}
cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
+#ifndef CONFIG_64BIT
+ smp_wmb();
+ cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
+#endif
}
/*
@@ -1376,10 +1380,21 @@ static void task_waking_fair(struct task_struct *p)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ u64 min_vruntime;
- lockdep_assert_held(&task_rq(p)->lock);
+#ifndef CONFIG_64BIT
+ u64 min_vruntime_copy;
- se->vruntime -= cfs_rq->min_vruntime;
+ do {
+ min_vruntime_copy = cfs_rq->min_vruntime_copy;
+ smp_rmb();
+ min_vruntime = cfs_rq->min_vruntime;
+ } while (min_vruntime != min_vruntime_copy);
+#else
+ min_vruntime = cfs_rq->min_vruntime;
+#endif
+
+ se->vruntime -= min_vruntime;
}
#ifdef CONFIG_FAIR_GROUP_SCHED
--
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