diff options
| author | Trond Myklebust <Trond.Myklebust@netapp.com> | 2013-05-22 12:57:24 -0400 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-05-30 14:35:04 +0100 |
| commit | f7b72b71fe00b5159d71f0d385c8d5e5865bcd32 (patch) | |
| tree | efaa16d1b96ec549491db7cc4bc4f396bbe29fee | |
| parent | a27e05b0cf32d711c1ec57625b6053658efd11fc (diff) | |
SUNRPC: Prevent an rpc_task wakeup race
commit a3c3cac5d31879cd9ae2de7874dc6544ca704aec upstream.
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -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 150848bf717c..206c61eda924 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -299,11 +299,17 @@ 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); |