From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Fernandes Subject: Re: [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback Date: Fri, 18 Apr 2014 11:34:50 -0500 Message-ID: <5351542A.5080307@ti.com> References: <1397782610-7370-1-git-send-email-joelf@ti.com> <20140418085019.GN27282@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from comal.ext.ti.com ([198.47.26.152]:41888 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754398AbaDRQe6 (ORCPT ); Fri, 18 Apr 2014 12:34:58 -0400 In-Reply-To: <20140418085019.GN27282@n2100.arm.linux.org.uk> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Russell King - ARM Linux Cc: dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, davinci-linux-open-source@linux.davincidsp.com, Vinod Koul , Dan Williams On 04/18/2014 03:50 AM, Russell King - ARM Linux wrote: > On Thu, Apr 17, 2014 at 07:56:50PM -0500, Joel Fernandes wrote: >> Free the vd (virt descriptor) after the callback is called. In EDMA driver >> atleast which uses virt-dma, we make use of the desc during the callback and if >> its dangerously freed before the callback is called. I also noticed this in >> omap-dma dmaengine driver. > > You've missed the vital bit of information: why do you make use of the > descriptor afterwards? You shouldn't. omap-dma doesn't either. > > Once clients submit their request to DMA engine, they must not hold any > kind of reference to the descriptor other than the cookie. > Sorry, I confused edma/omap-dma callbacks for virt dma callbacks. Anyway, I think there is still a chance in edma that we refer to the echan->edesc pointer later on after virt-dma calls the free (in edma_execute), so I'll just NULL that out to be safe and submit a patch. Thanks. regards, -Joel