SUNRPC: Add trace_rpc_timeout_status()

For a long while we've wanted a tracepoint that fires when a major
timeout is reported in the system log. Such a tracepoint can be
attached to other actions that can take place when a timeout is
detected (eg, server or connection health assessment).
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

include/trace/events/sunrpc.h

@@ -261,6 +261,7 @@ DECLARE_EVENT_CLASS(rpc_task_status,
 DEFINE_RPC_STATUS_EVENT(call);
 DEFINE_RPC_STATUS_EVENT(bind);
 DEFINE_RPC_STATUS_EVENT(connect);
+DEFINE_RPC_STATUS_EVENT(timeout);
 
 TRACE_EVENT(rpc_request,
 	TP_PROTO(const struct rpc_task *task),

net/sunrpc/clnt.c

@@ -2398,7 +2398,7 @@ rpc_check_timeout(struct rpc_task *task)
 	if (xprt_adjust_timeout(task->tk_rqstp) == 0)
 		return;
 
-	dprintk("RPC: %5u call_timeout (major)\n", task->tk_pid);
+	trace_rpc_timeout_status(task);
 	task->tk_timeouts++;
 
 	if (RPC_IS_SOFTCONN(task) && !rpc_check_connected(task->tk_rqstp)) {