diff options
| author | Trond Myklebust <Trond.Myklebust@netapp.com> | 2013-05-22 12:57:24 -0400 |
|---|---|---|
| committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2013-05-22 14:55:32 -0400 |
| commit | a3c3cac5d31879cd9ae2de7874dc6544ca704aec (patch) | |
| tree | e6d14d14aaed37a5bc28a8a6ebd952a7a42f9aa6 | |
| parent | 774d5f14ee1ecac55f42a84ff35eb00b896b00b6 (diff) | |
SUNRPC: Prevent an rpc_task wakeup race
The lockless RPC_IS_QUEUED() test in __rpc_execute means that we need to
be careful about ordering the calls to rpc_test_and_set_running(task) and
rpc_clear_queued(task). If we get the order wrong, then we may end up
testing the RPC_TASK_RUNNING flag after __rpc_execute() has looped
and changed the state of the rpc_task.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org
| -rw-r--r-- | net/sunrpc/sched.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index f8529fc8e54..5356b120dbf 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -324,11 +324,17 @@ EXPORT_SYMBOL_GPL(__rpc_wait_for_completion_task); * Note: If the task is ASYNC, and is being made runnable after sitting on an * rpc_wait_queue, this must be called with the queue spinlock held to protect * the wait queue operation. + * Note the ordering of rpc_test_and_set_running() and rpc_clear_queued(), + * which is needed to ensure that __rpc_execute() doesn't loop (due to the + * lockless RPC_IS_QUEUED() test) before we've had a chance to test + * the RPC_TASK_RUNNING flag. */ static void rpc_make_runnable(struct rpc_task *task) { + bool need_wakeup = !rpc_test_and_set_running(task); + rpc_clear_queued(task); - if (rpc_test_and_set_running(task)) + if (!need_wakeup) return; if (RPC_IS_ASYNC(task)) { INIT_WORK(&task->u.tk_work, rpc_async_schedule); |