rhashtable: Fix race in rhashtable_destroy() and use regular work_struct (57699a40) · Commits · 戴 / test

When we put our declared work task in the global workqueue with schedule_delayed_work(), its delay parameter is always zero. Therefore, we should define a regular work in rhashtable structure instead of a delayed work. By the way, we add a condition to check whether resizing functions are NULL before cancelling the work, avoiding to cancel an uninitialized work. Lastly, while we wait for all work items we submitted before to run to completion with cancel_delayed_work(), ht->mutex has been taken in rhashtable_destroy(). Moreover, cancel_delayed_work() doesn't return until all work items are accomplished, and when work items are scheduled, the work's function - rht_deferred_worker() will be called. However, as rht_deferred_worker() also needs to acquire the lock, deadlock might happen at the moment as the lock is already held before. So if the cancel work function is moved out of the lock covered scope, this will avoid the deadlock. Fixes: ("rhashtable: Per bucket locks & deferred expansion/shrinking") Signed-off-by:

Ying Xue <ying.xue@windriver.com> Cc: Thomas Graf <tgraf@suug.ch> Acked-by:

Thomas Graf <tgraf@suug.ch> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/linux/rhashtable.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -119,7 +119,7 @@ struct rhashtable {
		atomic_t nelems;
		atomic_t shift;
		struct rhashtable_params p;
		struct delayed_work run_work;
		struct work_struct run_work;
		struct mutex mutex;
		bool being_destroyed;
		};

lib/rhashtable.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -485,7 +485,7 @@ static void rht_deferred_worker(struct work_struct *work)
		struct rhashtable *ht;
		struct bucket_table *tbl;

		ht = container_of(work, struct rhashtable, run_work.work);
		ht = container_of(work, struct rhashtable, run_work);
		mutex_lock(&ht->mutex);
		tbl = rht_dereference(ht->tbl, ht);

		@@ -507,7 +507,7 @@ static void rhashtable_wakeup_worker(struct rhashtable *ht)
		if (tbl == new_tbl &&
		((ht->p.grow_decision && ht->p.grow_decision(ht, size)) \|\|
		(ht->p.shrink_decision && ht->p.shrink_decision(ht, size))))
		schedule_delayed_work(&ht->run_work, 0);
		schedule_work(&ht->run_work);
		}

		static void __rhashtable_insert(struct rhashtable ht, struct rhash_head obj,
		@@ -903,7 +903,7 @@ int rhashtable_init(struct rhashtable ht, struct rhashtable_params params)
		get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd));

		if (ht->p.grow_decision \|\| ht->p.shrink_decision)
		INIT_DEFERRABLE_WORK(&ht->run_work, rht_deferred_worker);
		INIT_WORK(&ht->run_work, rht_deferred_worker);

		return 0;
		}
		@@ -921,11 +921,11 @@ void rhashtable_destroy(struct rhashtable *ht)
		{
		ht->being_destroyed = true;

		mutex_lock(&ht->mutex);
		if (ht->p.grow_decision \|\| ht->p.shrink_decision)
		cancel_work_sync(&ht->run_work);

		cancel_delayed_work(&ht->run_work);
		mutex_lock(&ht->mutex);
		bucket_table_free(rht_dereference(ht->tbl, ht));

		mutex_unlock(&ht->mutex);
		}
		EXPORT_SYMBOL_GPL(rhashtable_destroy);

Admin message