From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Marciniszyn Subject: [PATCH] IB/hfi1: Avoid hardlockup with flushlist_lock Date: Mon, 24 Jun 2019 12:26:23 -0400 Message-ID: <20190624162623.184356.72785.stgit@awfm-01.aw.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Sender: stable-owner@vger.kernel.org To: stable@vger.kernel.org Cc: linux-rdma@vger.kernel.org, stable-commits@vger.kernel.org List-Id: linux-rdma@vger.kernel.org commit cf131a81967583ae737df6383a0893b9fee75b4e upstream. Heavy contention of the sde flushlist_lock can cause hard lockups at extreme scale when the flushing logic is under stress. Mitigate by replacing the item at a time copy to the local list with an O(1) list_splice_init() and using the high priority work queue to do the flushes. Ported to linux-4.19.y. Fixes: 7724105686e7 ("IB/hfi1: add driver files") Cc: Reviewed-by: Dennis Dalessandro Signed-off-by: Mike Marciniszyn Signed-off-by: Dennis Dalessandro Signed-off-by: Doug Ledford --- drivers/infiniband/hw/hfi1/sdma.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/drivers/infiniband/hw/hfi1/sdma.c b/drivers/infiniband/hw/hfi1/sdma.c index 88e326d..d648a41 100644 --- a/drivers/infiniband/hw/hfi1/sdma.c +++ b/drivers/infiniband/hw/hfi1/sdma.c @@ -410,10 +410,7 @@ static void sdma_flush(struct sdma_engine *sde) sdma_flush_descq(sde); spin_lock_irqsave(&sde->flushlist_lock, flags); /* copy flush list */ - list_for_each_entry_safe(txp, txp_next, &sde->flushlist, list) { - list_del_init(&txp->list); - list_add_tail(&txp->list, &flushlist); - } + list_splice_init(&sde->flushlist, &flushlist); spin_unlock_irqrestore(&sde->flushlist_lock, flags); /* flush from flush list */ list_for_each_entry_safe(txp, txp_next, &flushlist, list) @@ -2426,7 +2423,7 @@ int sdma_send_txreq(struct sdma_engine *sde, wait->tx_count++; wait->count += tx->num_desc; } - schedule_work(&sde->flush_worker); + queue_work_on(sde->cpu, system_highpri_wq, &sde->flush_worker); ret = -ECOMM; goto unlock; nodesc: @@ -2526,7 +2523,7 @@ int sdma_send_txlist(struct sdma_engine *sde, struct iowait *wait, } } spin_unlock(&sde->flushlist_lock); - schedule_work(&sde->flush_worker); + queue_work_on(sde->cpu, system_highpri_wq, &sde->flush_worker); ret = -ECOMM; goto update_tail; nodesc: