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Commit b247bbf1 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

SUNRPC: Fix a race in rpciod_down() 



The commit 4ada539e lead to the unpleasant
possibility of an asynchronous rpc_task being required to call
rpciod_down() when it is complete. This again means that the rpciod
workqueue may get to call destroy_workqueue on itself -> hang...

Change rpciod_up/rpciod_down to just get/put the module, and then
create/destroy the workqueues on module load/unload.

Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 4a2a4df7

net/sunrpc/sched.c

+23 −34
Original line number Original line Diff line number Diff line
@@ -50,8 +50,6 @@ static RPC_WAITQ(delay_queue, "delayq"); 
/*

/*

 * rpciod-related stuff

 * rpciod-related stuff

 */

 */

static DEFINE_MUTEX(rpciod_mutex);

static atomic_t rpciod_users = ATOMIC_INIT(0);

struct workqueue_struct *rpciod_workqueue;

struct workqueue_struct *rpciod_workqueue;





/*

/*
@@ -961,60 +959,49 @@ void rpc_killall_tasks(struct rpc_clnt *clnt) 
	spin_unlock(&clnt->cl_lock);

	spin_unlock(&clnt->cl_lock);

}

}





int rpciod_up(void)

{

	return try_module_get(THIS_MODULE) ? 0 : -EINVAL;

}



void rpciod_down(void)

{

	module_put(THIS_MODULE);

}



/*

/*

 * Start up the rpciod process if it's not already running.

 * Start up the rpciod workqueue.

 */

 */

int

static int rpciod_start(void)

rpciod_up(void)

{

{

	struct workqueue_struct *wq;

	struct workqueue_struct *wq;

	int error = 0;



	if (atomic_inc_not_zero(&rpciod_users))

		return 0;





	mutex_lock(&rpciod_mutex);



	/* Guard against races with rpciod_down() */

	if (rpciod_workqueue != NULL)

		goto out_ok;

	/*

	/*

	 * Create the rpciod thread and wait for it to start.

	 * Create the rpciod thread and wait for it to start.

	 */

	 */

	dprintk("RPC:       creating workqueue rpciod\n");

	dprintk("RPC:       creating workqueue rpciod\n");

	error = -ENOMEM;

	wq = create_workqueue("rpciod");

	wq = create_workqueue("rpciod");

	if (wq == NULL)

		goto out;



	rpciod_workqueue = wq;

	rpciod_workqueue = wq;

	error = 0;

	return rpciod_workqueue != NULL;

out_ok:

	atomic_inc(&rpciod_users);

out:

	mutex_unlock(&rpciod_mutex);

	return error;

}

}





void

static void rpciod_stop(void)

rpciod_down(void)

{

{

	if (!atomic_dec_and_test(&rpciod_users))

	struct workqueue_struct *wq = NULL;

		return;





	mutex_lock(&rpciod_mutex);

	if (rpciod_workqueue == NULL)

		return;

	dprintk("RPC:       destroying workqueue rpciod\n");

	dprintk("RPC:       destroying workqueue rpciod\n");





	if (atomic_read(&rpciod_users) == 0 && rpciod_workqueue != NULL) {

	wq = rpciod_workqueue;

		destroy_workqueue(rpciod_workqueue);

	rpciod_workqueue = NULL;

	rpciod_workqueue = NULL;

	}

	destroy_workqueue(wq);

	mutex_unlock(&rpciod_mutex);

}

}





void

void

rpc_destroy_mempool(void)

rpc_destroy_mempool(void)

{

{

	rpciod_stop();

	if (rpc_buffer_mempool)

	if (rpc_buffer_mempool)

		mempool_destroy(rpc_buffer_mempool);

		mempool_destroy(rpc_buffer_mempool);

	if (rpc_task_mempool)

	if (rpc_task_mempool)
@@ -1048,6 +1035,8 @@ rpc_init_mempool(void) 
						      rpc_buffer_slabp);

						      rpc_buffer_slabp);

	if (!rpc_buffer_mempool)

	if (!rpc_buffer_mempool)

		goto err_nomem;

		goto err_nomem;

	if (!rpciod_start())

		goto err_nomem;

	return 0;

	return 0;

err_nomem:

err_nomem:

	rpc_destroy_mempool();

	rpc_destroy_mempool();