Commit 89c5509b authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: separate out put_css_set_locked() and remove put_css_set_taskexit() 



put_css_set() is performed in two steps - it first tries to put
without grabbing css_set_rwsem if such put wouldn't make the count
zero.  If that fails, it puts after write-locking css_set_rwsem.  This
patch separates out the second phase into put_css_set_locked() which
should be called with css_set_rwsem locked.

Also, put_css_set_taskexit() is droped and put_css_set() is made to
take @taskexit.  There are only a handful users of these functions.
No point in providing different variants.

put_css_locked() will be used by later changes.  This patch doesn't
introduce any functional changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 889ed9ce

kernel/cgroup.c

+23 −27
Original line number Diff line number Diff line
@@ -369,22 +369,14 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) 
	return key;

}



static void __put_css_set(struct css_set *cset, int taskexit)

static void put_css_set_locked(struct css_set *cset, bool taskexit)

{

	struct cgrp_cset_link *link, *tmp_link;



	/*

	 * Ensure that the refcount doesn't hit zero while any readers

	 * can see it. Similar to atomic_dec_and_lock(), but for an

	 * rwlock

	 */

	if (atomic_add_unless(&cset->refcount, -1, 1))

		return;

	down_write(&css_set_rwsem);

	if (!atomic_dec_and_test(&cset->refcount)) {

		up_write(&css_set_rwsem);

	lockdep_assert_held(&css_set_rwsem);



	if (!atomic_dec_and_test(&cset->refcount))

		return;

	}



	/* This css_set is dead. unlink it and release cgroup refcounts */

	hash_del(&cset->hlist);
@@ -406,26 +398,30 @@ static void __put_css_set(struct css_set *cset, int taskexit) 
		kfree(link);

	}



	up_write(&css_set_rwsem);

	kfree_rcu(cset, rcu_head);

}



static void put_css_set(struct css_set *cset, bool taskexit)

{

	/*

 * refcounted get/put for css_set objects

	 * Ensure that the refcount doesn't hit zero while any readers

	 * can see it. Similar to atomic_dec_and_lock(), but for an

	 * rwlock

	 */

static inline void get_css_set(struct css_set *cset)

{

	atomic_inc(&cset->refcount);

}

	if (atomic_add_unless(&cset->refcount, -1, 1))

		return;



static inline void put_css_set(struct css_set *cset)

{

	__put_css_set(cset, 0);

	down_write(&css_set_rwsem);

	put_css_set_locked(cset, taskexit);

	up_write(&css_set_rwsem);

}



static inline void put_css_set_taskexit(struct css_set *cset)

/*

 * refcounted get/put for css_set objects

 */

static inline void get_css_set(struct css_set *cset)

{

	__put_css_set(cset, 1);

	atomic_inc(&cset->refcount);

}



/**
@@ -1752,7 +1748,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, 
	 * we're safe to drop it here; it will be freed under RCU.

	 */

	set_bit(CGRP_RELEASABLE, &old_cgrp->flags);

	put_css_set(old_cset);

	put_css_set(old_cset, false);

}



/**
@@ -1898,7 +1894,7 @@ out_put_css_set_refs: 
			tc = flex_array_get(group, i);

			if (!tc->cset)

				break;

			put_css_set(tc->cset);

			put_css_set(tc->cset, false);

		}

	}

out_cancel_attach:
@@ -3715,7 +3711,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) 


	/*

	 * css_set_rwsem synchronizes access to ->cset_links and prevents

	 * @cgrp from being removed while __put_css_set() is in progress.

	 * @cgrp from being removed while put_css_set() is in progress.

	 */

	down_read(&css_set_rwsem);

	empty = list_empty(&cgrp->cset_links);
@@ -4267,7 +4263,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks) 
	}

	task_unlock(tsk);



	put_css_set_taskexit(cset);

	put_css_set(cset, true);

}



static void check_for_release(struct cgroup *cgrp)

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