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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>
This commit is contained in:
Lai Jiangshan 2009-01-07 18:08:39 -08:00 committed by Linus Torvalds
parent e7c5ec9193
commit 13337714f3
1 changed files with 3 additions and 8 deletions
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11
kernel/cpuset.c
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@ -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();
}
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);