From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936298AbcIFXDr (ORCPT ); Tue, 6 Sep 2016 19:03:47 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:48971 "HELO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S933172AbcIFXDo (ORCPT ); Tue, 6 Sep 2016 19:03:44 -0400 From: "Rafael J. Wysocki" To: Marek Szyprowski Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Joerg Roedel , Inki Dae , Kukjin Kim , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , Ulf Hansson , Mark Brown , Greg Kroah-Hartman Subject: Re: [PATCH v2 06/10] driver core: Avoid endless recursion if device has more than one link Date: Wed, 07 Sep 2016 01:09:36 +0200 Message-ID: <1633380.7F0afK1dbG@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.8.0-rc2+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1466144820-6286-7-git-send-email-m.szyprowski@samsung.com> References: <1466144820-6286-1-git-send-email-m.szyprowski@samsung.com> <1466144820-6286-7-git-send-email-m.szyprowski@samsung.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, June 17, 2016 08:26:56 AM Marek Szyprowski wrote: > This patch fixes endless recursion, which happends when device has > more than one link. > > Signed-off-by: Marek Szyprowski > --- > drivers/base/core.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 215cd44de761..4e778539b750 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -57,7 +57,8 @@ static int device_reorder_to_tail(struct device *dev, void *not_used) > device_pm_move_last(dev); > device_for_each_child(dev, NULL, device_reorder_to_tail); > list_for_each_entry(link, &dev->consumer_links, c_node) > - device_reorder_to_tail(link->consumer, NULL); > + if (link->consumer != dev) > + device_reorder_to_tail(link->consumer, NULL); > > return 0; > } > If I'm not mistaken, this should not be necessary unless dev has a link pointing to itself as a consumer. That would be a bug, though. I can add a WARN_ON() to catch this case, but then if there's a link from a consumer of dev pointing back to dev as a consumer, that still will loop forever. I guess we need to detect circular dependencies and fail link creation in such cases. Oh well. Thanks, Rafael