cpuset: rcu_read_lock() to protect task_cs()

13337714 · Lai Jiangshan <[email protected]> · 2009-01-07 18:08:39 -08:00

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 <[email protected]>
Acked-by: Paul Menage <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Balbir Singh <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: 13337714f3b0307dc7f75ef5d83ecf0db2abbd65
Parents: e7c5ec91

Changes

1 files changed · +3 −8

File	Status	Add	Del	Content
kernel/cpuset.c	modified	+3	−8	View file

kernel/cpuset.c

View file

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 345ace5..a841b5c 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -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);