Commit 13337714 authored Jan 07, 2009 by Lai Jiangshan Committed by Linus Torvalds Jan 08, 2009

cpuset: rcu_read_lock() to protect task_cs()



task_cs() calls task_subsys_state().

We must use rcu_read_lock() to protect cgroup_subsys_state().

It's correct that top_cpuset is never freed, but cgroup_subsys_state()
accesses css_set, this css_set maybe freed when task_cs() called.

We use use rcu_read_lock() to protect it.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e7c5ec91

kernel/cpuset.c

+3 −8

Original line number	Diff line number	Diff line
		@@ -375,14 +375,9 @@ void cpuset_update_task_memory_state(void)
		struct task_struct *tsk = current;
		struct cpuset *cs;

		if (task_cs(tsk) == &top_cpuset) {
		/* Don't need rcu for top_cpuset. It's never freed. */
		my_cpusets_mem_gen = top_cpuset.mems_generation;
		} else {
		rcu_read_lock();
		my_cpusets_mem_gen = task_cs(tsk)->mems_generation;
		rcu_read_unlock();
		}

		if (my_cpusets_mem_gen != tsk->cpuset_mems_generation) {
		mutex_lock(&callback_mutex);