From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754517Ab3H1Gmq (ORCPT ); Wed, 28 Aug 2013 02:42:46 -0400 Received: from mga03.intel.com ([143.182.124.21]:39870 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753974Ab3H1Gmp (ORCPT ); Wed, 28 Aug 2013 02:42:45 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.89,974,1367996400"; d="scan'208";a="352616042" Date: Wed, 28 Aug 2013 11:27:38 +0530 From: Vinod Koul To: Lars-Peter Clausen Cc: Dan Williams , Jassi Brar , linux-kernel@vger.kernel.org Subject: Re: [PATCH resend] dma: pl330: Fix handling of TERMINATE_ALL while processing completed descriptors Message-ID: <20130828055738.GB11414@intel.com> References: <1377628445-16231-1-git-send-email-lars@metafoo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1377628445-16231-1-git-send-email-lars@metafoo.de> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 27, 2013 at 08:34:05PM +0200, Lars-Peter Clausen wrote: > The pl330 DMA driver is broken in regard to handling a terminate all request > while it is processing the list of completed descriptors. This is most visible > when calling dmaengine_terminate_all() from within the descriptors callback for > cyclic transfers. In this case the TERMINATE_ALL transfer will clear the > work_list and stop the transfer. But after all callbacks for all completed > descriptors have been handled the descriptors will be re-enqueued into the (now > empty) work_list. So the next time dma_async_issue_pending() is called for the > channel these descriptors will be transferred again which will cause data > corruption. Similar issues can occur if dmaengine_terminate_all() is not called > from within the descriptor callback but runs on a different CPU at the same time > as the completed descriptor list is processed. > > This patch introduces a new per channel list which will hold the completed > descriptors. While processing the list the channel's lock will be held to avoid > racing against dmaengine_terminate_all(). The lock will be released when calling > the descriptors callback though. Since the list of completed descriptors might > be modified (e.g. by calling dmaengine_terminate_all() from the callback) we can > not use the normal list iterator macros. Instead we'll need to check for each > loop iteration again if there are still items in the list. The drivers > TERMINATE_ALL implementation is updated to move descriptors from both the > work_list as well the new completed_list back to the descriptor pool. This makes > sure that none of the descripts finds its way back into the work list and also > that we do not call any futher complete callbacks after > dmaengine_terminate_all() has been called. Applied, thanks ~Vinod