cgroups: change css_set freeing mechanism to be under RCU (c378369d) · Commits · 戴 / test

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>

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);
		}

		/*

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