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SUNRPC: Fix potential races in xprt_lock_write_next()

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We have to ensure that the wake up from the waitqueue and the assignment
of xprt->snd_task are atomic. We can do this by assigning the snd_task
while under the waitqueue spinlock.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust
2012-01-17 22:57:37 -05:00
parent 2aeb98f498
commit 961a828df6
6 changed files with 79 additions and 46 deletions
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42
net/sunrpc/sched.c
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@ -422,7 +422,7 @@ EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);
/*
* Wake up the next task on a priority queue.
*/
static struct rpc_task * __rpc_wake_up_next_priority(struct rpc_wait_queue *queue)
static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *queue)
{
struct list_head *q;
struct rpc_task *task;
@ -467,30 +467,54 @@ new_queue:
new_owner:
rpc_set_waitqueue_owner(queue, task->tk_owner);
out:
rpc_wake_up_task_queue_locked(queue, task);
return task;
}
static struct rpc_task *__rpc_find_next_queued(struct rpc_wait_queue *queue)
{
if (RPC_IS_PRIORITY(queue))
return __rpc_find_next_queued_priority(queue);
if (!list_empty(&queue->tasks[0]))
return list_first_entry(&queue->tasks[0], struct rpc_task, u.tk_wait.list);
return NULL;
}
/*
* Wake up the next task on the wait queue.
* Wake up the first task on the wait queue.
*/
struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *queue,
bool (*func)(struct rpc_task *, void *), void *data)
{
struct rpc_task *task = NULL;
dprintk("RPC: wake_up_next(%p \"%s\")\n",
dprintk("RPC: wake_up_first(%p \"%s\")\n",
queue, rpc_qname(queue));
spin_lock_bh(&queue->lock);
if (RPC_IS_PRIORITY(queue))
task = __rpc_wake_up_next_priority(queue);
else {
task_for_first(task, &queue->tasks[0])
task = __rpc_find_next_queued(queue);
if (task != NULL) {
if (func(task, data))
rpc_wake_up_task_queue_locked(queue, task);
else
task = NULL;
}
spin_unlock_bh(&queue->lock);
return task;
}
EXPORT_SYMBOL_GPL(rpc_wake_up_first);
static bool rpc_wake_up_next_func(struct rpc_task *task, void *data)
{
return true;
}
/*
* Wake up the next task on the wait queue.
*/
struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue)
{
return rpc_wake_up_first(queue, rpc_wake_up_next_func, NULL);
}
EXPORT_SYMBOL_GPL(rpc_wake_up_next);
/**