RDMA/bnxt_re: Fix hang during driver unload

Driver unload hits a hang during stress testing of load/unload.

stack trace snippet -

tasklet_kill at ffffffff9aabb8b2
bnxt_qplib_nq_stop_irq at ffffffffc0a805fb [bnxt_re]
bnxt_qplib_disable_nq at ffffffffc0a80c5b [bnxt_re]
bnxt_re_dev_uninit at ffffffffc0a67d15 [bnxt_re]
bnxt_re_remove_device at ffffffffc0a6af1d [bnxt_re]

tasklet_kill can hang if the tasklet is scheduled after it is disabled.

Modified the sequences to disable the interrupt first and synchronize
irq before disabling the tasklet.

Fixes: 1ac5a40 ("RDMA/bnxt_re: Add bnxt_re RoCE driver")
Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Link: https://lore.kernel.org/r/1689322969-25402-3-git-send-email-selvin.xavier@broadcom.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Author: selvintxavier

drivers/infiniband/hw/bnxt_re/qplib_fp.c

@@ -420,19 +420,19 @@ void bnxt_qplib_nq_stop_irq(struct bnxt_qplib_nq *nq, bool kill)
 	if (!nq->requested)
 		return;
 
-	tasklet_disable(&nq->nq_tasklet);
+	nq->requested = false;
 	/* Mask h/w interrupt */
 	bnxt_qplib_ring_nq_db(&nq->nq_db.dbinfo, nq->res->cctx, false);
 	/* Sync with last running IRQ handler */
 	synchronize_irq(nq->msix_vec);
-	if (kill)
-		tasklet_kill(&nq->nq_tasklet);
-
 	irq_set_affinity_hint(nq->msix_vec, NULL);
 	free_irq(nq->msix_vec, nq);
 	kfree(nq->name);
 	nq->name = NULL;
-	nq->requested = false;
+
+	if (kill)
+		tasklet_kill(&nq->nq_tasklet);
+	tasklet_disable(&nq->nq_tasklet);
 }
 
 void bnxt_qplib_disable_nq(struct bnxt_qplib_nq *nq)

drivers/infiniband/hw/bnxt_re/qplib_rcfw.c

@@ -989,19 +989,18 @@ void bnxt_qplib_rcfw_stop_irq(struct bnxt_qplib_rcfw *rcfw, bool kill)
 	if (!creq->requested)
 		return;
 
-	tasklet_disable(&creq->creq_tasklet);
+	creq->requested = false;
 	/* Mask h/w interrupts */
 	bnxt_qplib_ring_nq_db(&creq->creq_db.dbinfo, rcfw->res->cctx, false);
 	/* Sync with last running IRQ-handler */
 	synchronize_irq(creq->msix_vec);
-	if (kill)
-		tasklet_kill(&creq->creq_tasklet);
-
 	free_irq(creq->msix_vec, rcfw);
 	kfree(creq->irq_name);
 	creq->irq_name = NULL;
-	creq->requested = false;
 	atomic_set(&rcfw->rcfw_intr_enabled, 0);
+	if (kill)
+		tasklet_kill(&creq->creq_tasklet);
+	tasklet_disable(&creq->creq_tasklet);
 }
 
 void bnxt_qplib_disable_rcfw_channel(struct bnxt_qplib_rcfw *rcfw)