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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB0E2EB64DD for ; Sun, 30 Jul 2023 23:51:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229562AbjG3Xun (ORCPT ); Sun, 30 Jul 2023 19:50:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229459AbjG3Xul (ORCPT ); Sun, 30 Jul 2023 19:50:41 -0400 Received: from ale.deltatee.com (ale.deltatee.com [204.191.154.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8634210C0; Sun, 30 Jul 2023 16:50:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:In-Reply-To:From:References:Cc:To: MIME-Version:Date:Message-ID:content-disposition; bh=FVsm7XR5gyD3MmGf40bx/+LP6XG63Sd/Pb98sroNX+0=; b=Pwizs9VhPURkngamp5j03F2HZb wDmxLfwou6NxEh4deJei7d1+l+mIoNhPDLeCGbdd/asUvPAoVTeF1ESYx+3WhOxFY0yAzaVbtJ3Pp P1kVY/PCF7uSpLEfBuCWXXywYnqfxWweu+xO7z69+/fa5sPD2/xLyL2Pnuw3ZMMSn3u4TuSSXhuJ9 5iUNlJpx/kuUw6UcTGpZTtKDnx3ZYDo5kFGwEbPGu3Ixu1E5gH4AfAJx2S0b4sdZAX+czi4mQWyL4 KP99IfaRg6xrO9RT/d2Qz+ssfo+9CP/JlzPkmrCBKCZifNILYE97hgoaA5hAw1d4zN02kfKg4U3jO YNm0HAjw==; Received: from s0106a84e3fe8c3f3.cg.shawcable.net ([24.64.144.200] helo=[192.168.0.10]) by ale.deltatee.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1qQGBF-00F0SV-Ve; Sun, 30 Jul 2023 17:50:34 -0600 Message-ID: Date: Sun, 30 Jul 2023 17:50:32 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.1 To: Chengfeng Ye , vkoul@kernel.org Cc: yuyunbo519@gmail.com, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, christophe.jaillet@wanadoo.fr References: <20230729175952.4068-1-dg573847474@gmail.com> Content-Language: en-CA From: Logan Gunthorpe In-Reply-To: <20230729175952.4068-1-dg573847474@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 24.64.144.200 X-SA-Exim-Rcpt-To: dg573847474@gmail.com, vkoul@kernel.org, yuyunbo519@gmail.com, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, christophe.jaillet@wanadoo.fr X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH v2] dmaengine: plx_dma: Fix potential deadlock on &plxdev->ring_lock X-SA-Exim-Version: 4.2.1 (built Sat, 13 Feb 2021 17:57:42 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/29/23 11:59, Chengfeng Ye wrote: > As plx_dma_process_desc() is invoked by both tasklet plx_dma_desc_task() > under softirq context and plx_dma_tx_status() callback that executed under > process context, the lock aquicision of &plxdev->ring_lock inside > plx_dma_process_desc() should disable irq otherwise deadlock could happen > if the irq preempts the execution of process context code while the lock > is held in process context on the same CPU. > > Possible deadlock scenario: > plx_dma_tx_status() > -> plx_dma_process_desc() > -> spin_lock(&plxdev->ring_lock) > > -> plx_dma_desc_task() > -> plx_dma_process_desc() > -> spin_lock(&plxdev->ring_lock) (deadlock here) > > This flaw was found by an experimental static analysis tool I am developing > for irq-related deadlock. > > The lock was changed from spin_lock_bh() to spin_lock() by a previous patch > for performance concern but unintentionally brought this potential deadlock > problem. > > This patch reverts back to spin_lock_bh() to fix the deadlock problem. > > Fixes: 1d05a0bdb420 ("dmaengine: plx_dma: Move spin_lock_bh() to spin_lock()") > Signed-off-by: Chengfeng Ye > Reviewed-by: Logan Gunthorpe Thanks! Logan