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SUNRPC: Fix a race in rpciod_down()

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The commit 4ada539ed7 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>
This commit is contained in:
Trond Myklebust 2007-07-19 16:32:20 -04:00
parent 4a2a4df7b6
commit b247bbf1da
1 changed files with 23 additions and 34 deletions
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57
net/sunrpc/sched.c
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@ -50,8 +50,6 @@ static RPC_WAITQ(delay_queue, "delayq");
/*
* 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 @@ void rpc_killall_tasks(struct rpc_clnt *clnt)
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_init_mempool(void)
rpc_buffer_slabp);
if (!rpc_buffer_mempool)
goto err_nomem;
if (!rpciod_start())
goto err_nomem;
return 0;
err_nomem:
rpc_destroy_mempool();