RDMA/rxe: Remove tasklet call from rxe_cq.c

Remove the tasklet call in rxe_cq.c and also the is_dying in the
cq struct. There is no reason for the rxe driver to defer the call
to the cq completion handler by scheduling a tasklet. rxe_cq_post()
is not called in a hard irq context.

The rxe driver currently is incorrect because the tasklet call is
made without protecting the cq pointer with a reference from having
the underlying memory freed before the deferred routine is called.
Executing the comp_handler inline fixes this problem.

Fixes: 8700e3e7 ("Soft RoCE driver")
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Link: https://lore.kernel.org/r/20230327215643.10410-1-rpearsonhpe@gmail.comAcked-by: Zhu Yanjun <zyjzyj2000@gmail.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/sw/rxe/rxe_cq.c

@@ -39,21 +39,6 @@ int rxe_cq_chk_attr(struct rxe_dev *rxe, struct rxe_cq *cq,
 	return -EINVAL;
 }
 
-static void rxe_send_complete(struct tasklet_struct *t)
-{
-	struct rxe_cq *cq = from_tasklet(cq, t, comp_task);
-	unsigned long flags;
-
-	spin_lock_irqsave(&cq->cq_lock, flags);
-	if (cq->is_dying) {
-		spin_unlock_irqrestore(&cq->cq_lock, flags);
-		return;
-	}
-	spin_unlock_irqrestore(&cq->cq_lock, flags);
-
-	cq->ibcq.comp_handler(&cq->ibcq, cq->ibcq.cq_context);
-}
-
 int rxe_cq_from_init(struct rxe_dev *rxe, struct rxe_cq *cq, int cqe,
 		     int comp_vector, struct ib_udata *udata,
 		     struct rxe_create_cq_resp __user *uresp)
@@ -79,10 +64,6 @@ int rxe_cq_from_init(struct rxe_dev *rxe, struct rxe_cq *cq, int cqe,
 
 	cq->is_user = uresp;
 
-	cq->is_dying = false;
-
-	tasklet_setup(&cq->comp_task, rxe_send_complete);
-
 	spin_lock_init(&cq->cq_lock);
 	cq->ibcq.cqe = cqe;
 	return 0;
@@ -103,6 +84,7 @@ int rxe_cq_resize_queue(struct rxe_cq *cq, int cqe,
 	return err;
 }
 
+/* caller holds reference to cq */
 int rxe_cq_post(struct rxe_cq *cq, struct rxe_cqe *cqe, int solicited)
 {
 	struct ib_event ev;
@@ -136,21 +118,13 @@ int rxe_cq_post(struct rxe_cq *cq, struct rxe_cqe *cqe, int solicited)
 	if ((cq->notify == IB_CQ_NEXT_COMP) ||
 	    (cq->notify == IB_CQ_SOLICITED && solicited)) {
 		cq->notify = 0;
-		tasklet_schedule(&cq->comp_task);
+
+		cq->ibcq.comp_handler(&cq->ibcq, cq->ibcq.cq_context);
 	}
 
 	return 0;
 }
 
-void rxe_cq_disable(struct rxe_cq *cq)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&cq->cq_lock, flags);
-	cq->is_dying = true;
-	spin_unlock_irqrestore(&cq->cq_lock, flags);
-}
-
 void rxe_cq_cleanup(struct rxe_pool_elem *elem)
 {
 	struct rxe_cq *cq = container_of(elem, typeof(*cq), elem);

drivers/infiniband/sw/rxe/rxe_verbs.c

@@ -1178,8 +1178,6 @@ static int rxe_destroy_cq(struct ib_cq *ibcq, struct ib_udata *udata)
 		goto err_out;
 	}
 
-	rxe_cq_disable(cq);
-
 	err = rxe_cleanup(cq);
 	if (err)
 		rxe_err_cq(cq, "cleanup failed, err = %d", err);

drivers/infiniband/sw/rxe/rxe_verbs.h

@@ -63,9 +63,7 @@ struct rxe_cq {
 	struct rxe_queue	*queue;
 	spinlock_t		cq_lock;
 	u8			notify;
-	bool			is_dying;
 	bool			is_user;
-	struct tasklet_struct	comp_task;
 	atomic_t		num_wq;
 };