[PATCH] RPC: Fix a race with rpc_restart_call()
If the task->tk_exit() wants to restart the RPC call after delaying
then the current RPC code will clobber the timer by calling
rpc_delete_timer() immediately after re-entering the loop in
__rpc_execute().
Problem noticed by Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index c06614d..cc298fa 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -555,6 +555,30 @@
}
/*
+ * Helper that calls task->tk_exit if it exists and then returns
+ * true if we should exit __rpc_execute.
+ */
+static inline int __rpc_do_exit(struct rpc_task *task)
+{
+ if (task->tk_exit != NULL) {
+ lock_kernel();
+ task->tk_exit(task);
+ unlock_kernel();
+ /* If tk_action is non-null, we should restart the call */
+ if (task->tk_action != NULL) {
+ if (!RPC_ASSASSINATED(task)) {
+ /* Release RPC slot and buffer memory */
+ xprt_release(task);
+ rpc_free(task);
+ return 0;
+ }
+ printk(KERN_ERR "RPC: dead task tried to walk away.\n");
+ }
+ }
+ return 1;
+}
+
+/*
* This is the RPC `scheduler' (or rather, the finite state machine).
*/
static int __rpc_execute(struct rpc_task *task)
@@ -566,8 +590,7 @@
BUG_ON(RPC_IS_QUEUED(task));
- restarted:
- while (1) {
+ for (;;) {
/*
* Garbage collection of pending timers...
*/
@@ -600,11 +623,12 @@
* by someone else.
*/
if (!RPC_IS_QUEUED(task)) {
- if (!task->tk_action)
+ if (task->tk_action != NULL) {
+ lock_kernel();
+ task->tk_action(task);
+ unlock_kernel();
+ } else if (__rpc_do_exit(task))
break;
- lock_kernel();
- task->tk_action(task);
- unlock_kernel();
}
/*
@@ -645,23 +669,6 @@
dprintk("RPC: %4d sync task resuming\n", task->tk_pid);
}
- if (task->tk_exit) {
- lock_kernel();
- task->tk_exit(task);
- unlock_kernel();
- /* If tk_action is non-null, the user wants us to restart */
- if (task->tk_action) {
- if (!RPC_ASSASSINATED(task)) {
- /* Release RPC slot and buffer memory */
- if (task->tk_rqstp)
- xprt_release(task);
- rpc_free(task);
- goto restarted;
- }
- printk(KERN_ERR "RPC: dead task tries to walk away.\n");
- }
- }
-
dprintk("RPC: %4d exit() = %d\n", task->tk_pid, task->tk_status);
status = task->tk_status;