lkml.org 
[lkml]   [2011]   [Dec]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:sched/core] sched, nohz: Fix missing RCU read lock
Commit-ID:  067491b7313c41f49607fce782d29344d1472587
Gitweb: http://git.kernel.org/tip/067491b7313c41f49607fce782d29344d1472587
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 7 Dec 2011 14:32:08 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 8 Dec 2011 05:45:48 +0100

sched, nohz: Fix missing RCU read lock

Yong Zhang reported:

> [ INFO: suspicious RCU usage. ]
> kernel/sched/fair.c:5091 suspicious rcu_dereference_check() usage!

This is due to the sched_domain stuff being RCU protected and
commit 0b005cf5 ("sched, nohz: Implement sched group, domain
aware nohz idle load balancing") overlooking this fact.

The sd variable only lives inside the for_each_domain() block,
so we only need to wrap that.

Reported-by: Yong Zhang <yong.zhang0@gmail.com>
Tested-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1323264728.32012.107.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched/fair.c | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6482136..a4d2b7a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5088,23 +5088,28 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu)
if (rq->nr_running >= 2)
goto need_kick;

+ rcu_read_lock();
for_each_domain(cpu, sd) {
struct sched_group *sg = sd->groups;
struct sched_group_power *sgp = sg->sgp;
int nr_busy = atomic_read(&sgp->nr_busy_cpus);

if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
- goto need_kick;
+ goto need_kick_unlock;

if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
&& (cpumask_first_and(nohz.idle_cpus_mask,
sched_domain_span(sd)) < cpu))
- goto need_kick;
+ goto need_kick_unlock;

if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
break;
}
+ rcu_read_unlock();
return 0;
+
+need_kick_unlock:
+ rcu_read_unlock();
need_kick:
return 1;
}

\
 
 \ /
  Last update: 2011-12-08 16:19    [W:0.395 / U:0.084 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site