From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66DF6C4BA24 for ; Thu, 27 Feb 2020 11:39:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3AC3C24693 for ; Thu, 27 Feb 2020 11:39:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582803574; bh=dsjaN6IEpMcr29Kc5SO3t+9YLNz9Fq1loVXo9eO4oi8=; h=From:To:Cc:Subject:Date:List-ID:From; b=p+M3oH5mlOQ/Db+o+RbBY/0Akj9M+0Dv5klQFh8ekR/aDhC+MKUuBoHIzfDWO8e3r hvzonpfHGrOR0lT/IaJZ3fk81STId9RJPkr5iTYAj+bRFs7TP+abX6W7LlTkmJaMLg ItNlXhPLjNJVCqTBoUTsbSuIYA1kK6YFLaO1mlQI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728856AbgB0Ljd (ORCPT ); Thu, 27 Feb 2020 06:39:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:48946 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728874AbgB0Ljd (ORCPT ); Thu, 27 Feb 2020 06:39:33 -0500 Received: from localhost (unknown [193.47.165.251]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3F33024690; Thu, 27 Feb 2020 11:39:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582803572; bh=dsjaN6IEpMcr29Kc5SO3t+9YLNz9Fq1loVXo9eO4oi8=; h=From:To:Cc:Subject:Date:From; b=L9jvqObYiJxSCOeGUw8598LiU58UuaKaa+0T5ONN7zk93fW1I2G/YDuIG6KKyWNBK 027MP8laSeIdBPpA16zbdbEhvN0SYsPVqpgjCiUvesXHgksqUtAhQCx1FOtyq+ZL+S 1RPn0T62mCc0XU/C10x80V/yNnJBplBa/wE2BWn4= From: Leon Romanovsky To: Doug Ledford , Jason Gunthorpe Cc: Artemy Kovalyov , linux-rdma@vger.kernel.org Subject: [PATCH rdma-rc] IB/mlx5: Fix implicit ODP race Date: Thu, 27 Feb 2020 13:39:18 +0200 Message-Id: <20200227113918.94432-1-leon@kernel.org> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org From: Artemy Kovalyov Following race may occur because of the call_srcu and the placement of the synchronize_srcu vs the xa_erase. CPU0 CPU1 mlx5_ib_free_implicit_mr: destroy_unused_implicit_child_mr: xa_erase(odp_mkeys) synchronize_srcu() xa_lock(implicit_children) if (still in xarray) atomic_inc() call_srcu() xa_unlock(implicit_children) xa_erase(implicit_children): xa_lock(implicit_children) __xa_erase() xa_unlock(implicit_children) flush_workqueue() [..] free_implicit_child_mr_rcu: (via call_srcu) queue_work() WARN_ON(atomic_read()) [..] free_implicit_child_mr_work: (via wq) free_implicit_child_mr() mlx5_mr_cache_invalidate() mlx5_ib_update_xlt() <-- UMR QP fail atomic_dec() The wait_event() solves the race because it blocks until free_implicit_child_mr_work() completes. Fixes: 5256edcb98a1 ("RDMA/mlx5: Rework implicit ODP destroy") Signed-off-by: Artemy Kovalyov Reviewed-by: Jason Gunthorpe Signed-off-by: Leon Romanovsky --- drivers/infiniband/hw/mlx5/mlx5_ib.h | 1 + drivers/infiniband/hw/mlx5/odp.c | 17 +++++++---------- 2 files changed, 8 insertions(+), 10 deletions(-) diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h index f21d446249b8..688dd4e28192 100644 --- a/drivers/infiniband/hw/mlx5/mlx5_ib.h +++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h @@ -636,6 +636,7 @@ struct mlx5_ib_mr { /* For ODP and implicit */ atomic_t num_deferred_work; + wait_queue_head_t q_deferred_work; struct xarray implicit_children; union { struct rcu_head rcu; diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c index 4216814ba871..bf50cd91f472 100644 --- a/drivers/infiniband/hw/mlx5/odp.c +++ b/drivers/infiniband/hw/mlx5/odp.c @@ -235,7 +235,8 @@ static void free_implicit_child_mr(struct mlx5_ib_mr *mr, bool need_imr_xlt) mr->parent = NULL; mlx5_mr_cache_free(mr->dev, mr); ib_umem_odp_release(odp); - atomic_dec(&imr->num_deferred_work); + if (atomic_dec_and_test(&imr->num_deferred_work)) + wake_up(&imr->q_deferred_work); } static void free_implicit_child_mr_work(struct work_struct *work) @@ -554,6 +555,7 @@ struct mlx5_ib_mr *mlx5_ib_alloc_implicit_mr(struct mlx5_ib_pd *pd, imr->umem = &umem_odp->umem; imr->is_odp_implicit = true; atomic_set(&imr->num_deferred_work, 0); + init_waitqueue_head(&imr->q_deferred_work); xa_init(&imr->implicit_children); err = mlx5_ib_update_xlt(imr, 0, @@ -611,10 +613,7 @@ void mlx5_ib_free_implicit_mr(struct mlx5_ib_mr *imr) * under xa_lock while the child is in the xarray. Thus at this point * it is only decreasing, and all work holding it is now on the wq. */ - if (atomic_read(&imr->num_deferred_work)) { - flush_workqueue(system_unbound_wq); - WARN_ON(atomic_read(&imr->num_deferred_work)); - } + wait_event(imr->q_deferred_work, !atomic_read(&imr->num_deferred_work)); /* * Fence the imr before we destroy the children. This allows us to @@ -645,10 +644,7 @@ void mlx5_ib_fence_odp_mr(struct mlx5_ib_mr *mr) /* Wait for all running page-fault handlers to finish. */ synchronize_srcu(&mr->dev->odp_srcu); - if (atomic_read(&mr->num_deferred_work)) { - flush_workqueue(system_unbound_wq); - WARN_ON(atomic_read(&mr->num_deferred_work)); - } + wait_event(mr->q_deferred_work, !atomic_read(&mr->num_deferred_work)); dma_fence_odp_mr(mr); } @@ -1720,7 +1716,8 @@ static void destroy_prefetch_work(struct prefetch_mr_work *work) u32 i; for (i = 0; i < work->num_sge; ++i) - atomic_dec(&work->frags[i].mr->num_deferred_work); + if (atomic_dec_and_test(&work->frags[i].mr->num_deferred_work)) + wake_up(&work->frags[i].mr->q_deferred_work); kvfree(work); } -- 2.24.1