From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162883AbcG1Dlk (ORCPT ); Wed, 27 Jul 2016 23:41:40 -0400 Received: from mga01.intel.com ([192.55.52.88]:57209 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758967AbcG1Dla (ORCPT ); Wed, 27 Jul 2016 23:41:30 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,433,1464678000"; d="scan'208";a="1030537818" Date: Thu, 28 Jul 2016 09:18:43 +0530 From: Vinod Koul To: Viresh Kumar Cc: Dan Williams , linaro-kernel@lists.linaro.org, Greg Kroah-Hartman , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dmaengine: device must have at least one channel Message-ID: <20160728034843.GI9681@localhost> References: <4a6e2283fb7736c33fb733c310314d7bc135cd6d.1469654853.git.viresh.kumar@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4a6e2283fb7736c33fb733c310314d7bc135cd6d.1469654853.git.viresh.kumar@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 27, 2016 at 02:32:58PM -0700, Viresh Kumar wrote: > The DMA device can't be registered if it doesn't have any channels > registered at all. Moreover, it leads to memory leak and is reported by > kmemleak as (on 3.10 kernel, and same shall happen on mainline): > > unreferenced object 0xffffffc09e597240 (size 64): > comm "swapper/0", pid 1, jiffies 4294877736 (age 7060.280s) > hex dump (first 32 bytes): > 00 00 00 00 c0 ff ff ff 30 00 00 ff 00 00 00 ff ........0....... > 00 00 00 ff 00 00 00 ff 00 00 00 ff 00 00 00 ff ................ > backtrace: > [] create_object+0x148/0x2a0 > [] kmemleak_alloc+0x80/0xbc > [] kmem_cache_alloc_trace+0x120/0x1ac > [] dma_async_device_register+0x160/0x46c > [] foo_probe+0x1a0/0x264 > [] platform_drv_probe+0x14/0x20 > [] driver_probe_device+0x160/0x374 > [] __driver_attach+0x60/0x90 > [] bus_for_each_dev+0x7c/0xb0 > [] driver_attach+0x1c/0x28 > [] bus_add_driver+0x124/0x248 > [] driver_register+0x90/0x110 > [] platform_driver_register+0x58/0x64 > [] foo_driver_init+0x10/0x1c > [] do_one_initcall+0xac/0x148 > [] kernel_init_freeable+0x1a0/0x258 > > Return -ENODEV from dma_async_device_register() on such a case. > > Signed-off-by: Viresh Kumar > --- > Hi Vinod, > > Sorry if the fundamentals behind this patch are completely incorrect, > i.e. We *can't* register a dma device with 0 channels. Its been long > that I have worked on dma stuff :) This sounds okay, but why would anyone register a device without having a channel? > > drivers/dma/dmaengine.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c > index 8c9f45fd55fc..6b535262ac5d 100644 > --- a/drivers/dma/dmaengine.c > +++ b/drivers/dma/dmaengine.c > @@ -997,6 +997,13 @@ int dma_async_device_register(struct dma_device *device) > } > chan->client_count = 0; > } > + > + if (!chancnt) { > + dev_err(device->dev, "%s: device has no channels!\n", __func__); > + rc = -ENODEV; > + goto err_out; > + } > + > device->chancnt = chancnt; > > mutex_lock(&dma_list_mutex); > -- > 2.7.4 > -- ~Vinod