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Commit c378369d authored by Ben Blum's avatar Ben Blum Committed by Linus Torvalds
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cgroups: change css_set freeing mechanism to be under RCU 



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: default avatarBen Blum <bblum@google.com>
Signed-off-by: default avatarPaul Menage <menage@google.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Acked-by: default avatarLi 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d1d9fd33

include/linux/cgroup.h

+3 −0
Original line number Diff line number Diff line
@@ -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

+7 −1
Original line number Diff line number Diff line
@@ -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);

}



/*