The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8ac0e6641c7ca14833a2a8c6f13d8e0a435e535c Mon Sep 17 00:00:00 2001

From: Zhu Yanjun yanjunz@mellanox.com Date: Wed, 12 Feb 2020 09:26:33 +0200 Subject: [PATCH] RDMA/rxe: Fix soft lockup problem due to using tasklets in softirq

When run stress tests with RXE, the following Call Traces often occur

watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [swapper/2:0] ... Call Trace: <IRQ> create_object+0x3f/0x3b0 kmem_cache_alloc_node_trace+0x129/0x2d0 __kmalloc_reserve.isra.52+0x2e/0x80 __alloc_skb+0x83/0x270 rxe_init_packet+0x99/0x150 [rdma_rxe] rxe_requester+0x34e/0x11a0 [rdma_rxe] rxe_do_task+0x85/0xf0 [rdma_rxe] tasklet_action_common.isra.21+0xeb/0x100 __do_softirq+0xd0/0x298 irq_exit+0xc5/0xd0 smp_apic_timer_interrupt+0x68/0x120 apic_timer_interrupt+0xf/0x20 </IRQ> ...

The root cause is that tasklet is actually a softirq. In a tasklet handler, another softirq handler is triggered. Usually these softirq handlers run on the same cpu core. So this will cause "soft lockup Bug".

Fixes: 8700e3e7c485 ("Soft RoCE driver") Link: https://lore.kernel.org/r/20200212072635.682689-8-leon@kernel.org Signed-off-by: Zhu Yanjun yanjunz@mellanox.com Signed-off-by: Leon Romanovsky leonro@mellanox.com Signed-off-by: Jason Gunthorpe jgg@mellanox.com

diff --git a/drivers/infiniband/sw/rxe/rxe_comp.c b/drivers/infiniband/sw/rxe/rxe_comp.c index 116cafc9afcf..4bc88708b355 100644 --- a/drivers/infiniband/sw/rxe/rxe_comp.c +++ b/drivers/infiniband/sw/rxe/rxe_comp.c @@ -329,7 +329,7 @@ static inline enum comp_state check_ack(struct rxe_qp *qp, qp->comp.psn = pkt->psn; if (qp->req.wait_psn) { qp->req.wait_psn = 0; - rxe_run_task(&qp->req.task, 1); + rxe_run_task(&qp->req.task, 0); } } return COMPST_ERROR_RETRY; @@ -463,7 +463,7 @@ static void do_complete(struct rxe_qp *qp, struct rxe_send_wqe *wqe) */ if (qp->req.wait_fence) { qp->req.wait_fence = 0; - rxe_run_task(&qp->req.task, 1); + rxe_run_task(&qp->req.task, 0); } }

@@ -479,7 +479,7 @@ static inline enum comp_state complete_ack(struct rxe_qp *qp, if (qp->req.need_rd_atomic) { qp->comp.timeout_retry = 0; qp->req.need_rd_atomic = 0; - rxe_run_task(&qp->req.task, 1); + rxe_run_task(&qp->req.task, 0); } }

@@ -725,7 +725,7 @@ int rxe_completer(void *arg) RXE_CNT_COMP_RETRY); qp->req.need_retry = 1; qp->comp.started_retry = 1; - rxe_run_task(&qp->req.task, 1); + rxe_run_task(&qp->req.task, 0); }

if (pkt) {