RDMA/rxe: Remove __rxe_do_task()

The subroutine __rxe_do_task is not thread safe and it has no way to
guarantee that the tasks, which are designed with the assumption that they
are non-reentrant, are not reentered. All of its uses are non-performance
critical.

This patch replaces calls to __rxe_do_task with calls to
rxe_sched_task. It also removes irrelevant or unneeded if tests.

Instead of calling the task machinery a single call to the tasklet
function (rxe_requester, etc.) is sufficient to draing the queues if task
execution has been disabled or stopped.

Together these changes allow the removal of __rxe_do_task.

Link: https://lore.kernel.org/r/20230304174533.11296-7-rpearsonhpe@gmail.comSigned-off-by: Ian Ziemba <ian.ziemba@hpe.com>
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_qp.c

@@ -473,29 +473,23 @@ static void rxe_qp_reset(struct rxe_qp *qp)
 {
 	/* stop tasks from running */
 	rxe_disable_task(&qp->resp.task);
-
-	/* stop request/comp */
-	if (qp->sq.queue) {
-		if (qp_type(qp) == IB_QPT_RC)
-			rxe_disable_task(&qp->comp.task);
-		rxe_disable_task(&qp->req.task);
-	}
+	rxe_disable_task(&qp->comp.task);
+	rxe_disable_task(&qp->req.task);
 
 	/* move qp to the reset state */
 	qp->req.state = QP_STATE_RESET;
 	qp->comp.state = QP_STATE_RESET;
 	qp->resp.state = QP_STATE_RESET;
 
-	/* let state machines reset themselves drain work and packet queues
-	 * etc.
-	 */
-	__rxe_do_task(&qp->resp.task);
+	/* drain work and packet queuesc */
+	rxe_requester(qp);
+	rxe_completer(qp);
+	rxe_responder(qp);
 
-	if (qp->sq.queue) {
-		__rxe_do_task(&qp->comp.task);
-		__rxe_do_task(&qp->req.task);
+	if (qp->rq.queue)
+		rxe_queue_reset(qp->rq.queue);
+	if (qp->sq.queue)
 		rxe_queue_reset(qp->sq.queue);
-	}
 
 	/* cleanup attributes */
 	atomic_set(&qp->ssn, 0);
@@ -518,13 +512,8 @@ static void rxe_qp_reset(struct rxe_qp *qp)
 
 	/* reenable tasks */
 	rxe_enable_task(&qp->resp.task);
-
-	if (qp->sq.queue) {
-		if (qp_type(qp) == IB_QPT_RC)
-			rxe_enable_task(&qp->comp.task);
-
-		rxe_enable_task(&qp->req.task);
-	}
+	rxe_enable_task(&qp->comp.task);
+	rxe_enable_task(&qp->req.task);
 }
 
 /* drain the send queue */
@@ -533,10 +522,7 @@ static void rxe_qp_drain(struct rxe_qp *qp)
 	if (qp->sq.queue) {
 		if (qp->req.state != QP_STATE_DRAINED) {
 			qp->req.state = QP_STATE_DRAIN;
-			if (qp_type(qp) == IB_QPT_RC)
-				rxe_sched_task(&qp->comp.task);
-			else
-				__rxe_do_task(&qp->comp.task);
+			rxe_sched_task(&qp->comp.task);
 			rxe_sched_task(&qp->req.task);
 		}
 	}
@@ -552,11 +538,7 @@ void rxe_qp_error(struct rxe_qp *qp)
 
 	/* drain work and packet queues */
 	rxe_sched_task(&qp->resp.task);
-
-	if (qp_type(qp) == IB_QPT_RC)
-		rxe_sched_task(&qp->comp.task);
-	else
-		__rxe_do_task(&qp->comp.task);
+	rxe_sched_task(&qp->comp.task);
 	rxe_sched_task(&qp->req.task);
 }
 
@@ -773,24 +755,20 @@ static void rxe_qp_do_cleanup(struct work_struct *work)
 
 	qp->valid = 0;
 	qp->qp_timeout_jiffies = 0;
-	rxe_cleanup_task(&qp->resp.task);
 
 	if (qp_type(qp) == IB_QPT_RC) {
 		del_timer_sync(&qp->retrans_timer);
 		del_timer_sync(&qp->rnr_nak_timer);
 	}
 
+	rxe_cleanup_task(&qp->resp.task);
 	rxe_cleanup_task(&qp->req.task);
 	rxe_cleanup_task(&qp->comp.task);
 
 	/* flush out any receive wr's or pending requests */
-	if (qp->req.task.func)
-		__rxe_do_task(&qp->req.task);
-
-	if (qp->sq.queue) {
-		__rxe_do_task(&qp->comp.task);
-		__rxe_do_task(&qp->req.task);
-	}
+	rxe_requester(qp);
+	rxe_completer(qp);
+	rxe_responder(qp);
 
 	if (qp->sq.queue)
 		rxe_queue_cleanup(qp->sq.queue);

drivers/infiniband/sw/rxe/rxe_task.c

@@ -6,19 +6,6 @@
 
 #include "rxe.h"
 
-int __rxe_do_task(struct rxe_task *task)
-
-{
-	int ret;
-
-	while ((ret = task->func(task->qp)) == 0)
-		;
-
-	task->ret = ret;
-
-	return ret;
-}
-
 /*
  * this locking is due to a potential race where
  * a second caller finds the task already running

drivers/infiniband/sw/rxe/rxe_task.h

@@ -39,12 +39,6 @@ int rxe_init_task(struct rxe_task *task, struct rxe_qp *qp,
 /* cleanup task */
 void rxe_cleanup_task(struct rxe_task *task);
 
-/*
- * raw call to func in loop without any checking
- * can call when tasklets are disabled
- */
-int __rxe_do_task(struct rxe_task *task);
-
 void rxe_run_task(struct rxe_task *task);
 
 void rxe_sched_task(struct rxe_task *task);