cgroups: change css_set freeing mechanism to be under RCU

c378369d · Ben Blum <[email protected]> · 2009-09-23 15:56:29 -07:00

Changes css_set freeing mechanism to be under RCU

This is a prepatch for making the procs file writable. In order to free the
old css_sets for each task to be moved as they're being moved, the freeing
mechanism must be RCU-protected, or else we would have to have a call to
synchronize_rcu() for each task before freeing its old css_set.

Signed-off-by: Ben Blum <[email protected]>
Signed-off-by: Paul Menage <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Acked-by: Li Zefan <[email protected]>
Cc: Matt Helsley <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: c378369d8b4fa516ff2b1e79c3eded4e0e955ebb
Parents: d1d9fd33

Changes

2 files changed · +10 −1

File	Status	Add	Del	Content
include/linux/cgroup.h	modified	+3	−0	View file
kernel/cgroup.c	modified	+7	−1	View file

include/linux/cgroup.h

View file

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 88e8634..3ac78a2 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -260,6 +260,9 @@ struct css_set {
 	 * during subsystem registration (at boot time).
 	 */
 	struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
+
+	/* For RCU-protected deletion */
+	struct rcu_head rcu_head;
 };
 
 /*

kernel/cgroup.c

View file

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 3e356b0..bf8dd1a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -267,6 +267,12 @@ static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
 	return &css_set_table[index];
 }
 
+static void free_css_set_rcu(struct rcu_head *obj)
+{
+	struct css_set *cg = container_of(obj, struct css_set, rcu_head);
+	kfree(cg);
+}
+
 /* We don't maintain the lists running through each css_set to its
  * task until after the first call to cgroup_iter_start(). This
  * reduces the fork()/exit() overhead for people who have cgroups
@@ -310,7 +316,7 @@ static void __put_css_set(struct css_set *cg, int taskexit)
 	}
 
 	write_unlock(&css_set_lock);
-	kfree(cg);
+	call_rcu(&cg->rcu_head, free_css_set_rcu);
 }
 
 /*