[PATCH v2.6.34-rc5 10/12] sched: Fix an RCU warning in print_task()
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From: Paul E. McKenney on 23 Apr 2010 15:50 From: Li Zefan <lizf(a)cn.fujitsu.com> With CONFIG_PROVE_RCU=y, a warning can be triggered: $ cat /proc/sched_debug .... kernel/cgroup.c:1649 invoked rcu_dereference_check() without protection! .... Both cgroup_path() and task_group() should be called with either rcu_read_lock or cgroup_mutex held. The rcu_dereference_check() does include cgroup_lock_is_held(), so we know that this lock is not held. Therefore, in a CONFIG_PREEMPT kernel, to say nothing of a CONFIG_PREEMPT_RT kernel, the original code could have ended up copying a string out of the freelist. This patch inserts RCU read-side primitives needed to prevent this scenario. Signed-off-by: Li Zefan <lizf(a)cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck(a)linux.vnet.ibm.com> --- kernel/sched_debug.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c index 9b49db1..19be00b 100644 --- a/kernel/sched_debug.c +++ b/kernel/sched_debug.c @@ -114,7 +114,9 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p) { char path[64]; + rcu_read_lock(); cgroup_path(task_group(p)->css.cgroup, path, sizeof(path)); + rcu_read_unlock(); SEQ_printf(m, " %s", path); } #endif -- 1.7.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |