SUNRPC: Fix a race in rpciod_down()
The commit 4ada539ed77c7a2bbcb75cafbbd7bd8d2b9bef7b 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: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index b5723c2..954d7ec 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -50,8 +50,6 @@
/*
* rpciod-related stuff
*/
-static DEFINE_MUTEX(rpciod_mutex);
-static atomic_t rpciod_users = ATOMIC_INIT(0);
struct workqueue_struct *rpciod_workqueue;
/*
@@ -961,60 +959,49 @@
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
-rpciod_up(void)
+static int rpciod_start(void)
{
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.
*/
dprintk("RPC: creating workqueue rpciod\n");
- error = -ENOMEM;
wq = create_workqueue("rpciod");
- if (wq == NULL)
- goto out;
-
rpciod_workqueue = wq;
- error = 0;
-out_ok:
- atomic_inc(&rpciod_users);
-out:
- mutex_unlock(&rpciod_mutex);
- return error;
+ return rpciod_workqueue != NULL;
}
-void
-rpciod_down(void)
+static void rpciod_stop(void)
{
- if (!atomic_dec_and_test(&rpciod_users))
- return;
+ struct workqueue_struct *wq = NULL;
- mutex_lock(&rpciod_mutex);
+ if (rpciod_workqueue == NULL)
+ return;
dprintk("RPC: destroying workqueue rpciod\n");
- if (atomic_read(&rpciod_users) == 0 && rpciod_workqueue != NULL) {
- destroy_workqueue(rpciod_workqueue);
- rpciod_workqueue = NULL;
- }
- mutex_unlock(&rpciod_mutex);
+ wq = rpciod_workqueue;
+ rpciod_workqueue = NULL;
+ destroy_workqueue(wq);
}
void
rpc_destroy_mempool(void)
{
+ rpciod_stop();
if (rpc_buffer_mempool)
mempool_destroy(rpc_buffer_mempool);
if (rpc_task_mempool)
@@ -1048,6 +1035,8 @@
rpc_buffer_slabp);
if (!rpc_buffer_mempool)
goto err_nomem;
+ if (!rpciod_start())
+ goto err_nomem;
return 0;
err_nomem:
rpc_destroy_mempool();