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cgroups: change css_set freeing mechanism to be under RCU

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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 <bblum@google.com>
Signed-off-by: Paul Menage <menage@google.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ben Blum 2009-09-23 15:56:29 -07:00 committed by Linus Torvalds
parent d1d9fd3308
commit c378369d8b
2 changed files with 10 additions and 1 deletions
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3
include/linux/cgroup.h
View file

@ -260,6 +260,9 @@ struct css_set {
* during subsystem registration (at boot time). * during subsystem registration (at boot time).
*/ */
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT]; struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
/* For RCU-protected deletion */
struct rcu_head rcu_head;
}; };
/* /*

8
kernel/cgroup.c
View file

@ -267,6 +267,12 @@ static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
return &css_set_table[index]; 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 /* We don't maintain the lists running through each css_set to its
* task until after the first call to cgroup_iter_start(). This * task until after the first call to cgroup_iter_start(). This
* reduces the fork()/exit() overhead for people who have cgroups * 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); write_unlock(&css_set_lock);
kfree(cg); call_rcu(&cg->rcu_head, free_css_set_rcu);
} }
/* /*