SUNRPC: Fix a potential race in rpc_wake_up_task()

Use RCU to ensure that we can safely call rpc_finish_wakeup after we've
called __rpc_do_wake_up_task. If not, there is a theoretical race, in which
the rpc_task finishes executing, and gets freed first.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index 9fdb8c9d09f2..14fc813ddd0c 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -11,6 +11,7 @@
 
 #include <linux/timer.h>
 #include <linux/sunrpc/types.h>
+#include <linux/rcupdate.h>
 #include <linux/spinlock.h>
 #include <linux/wait.h>
 #include <linux/workqueue.h>
@@ -85,6 +86,7 @@ struct rpc_task {
         union {
                 struct work_struct      tk_work;        /* Async task work queue */
                 struct rpc_wait         tk_wait;        /* RPC wait */
+                struct rcu_head         tk_rcu;         /* for task deletion */
         } u;
 
         unsigned short          tk_timeouts;    /* maj timeouts */