From patchwork Wed Sep 9 22:15:18 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Simon Guinot X-Patchwork-Id: 516051 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 746A4140134 for ; Thu, 10 Sep 2015 08:15:28 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752283AbbIIWP1 (ORCPT ); Wed, 9 Sep 2015 18:15:27 -0400 Received: from vm1.sequanux.org ([188.165.36.56]:41861 "EHLO vm1.sequanux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751055AbbIIWP0 (ORCPT ); Wed, 9 Sep 2015 18:15:26 -0400 Received: from localhost (localhost.localdomain [127.0.0.1]) by vm1.sequanux.org (Postfix) with ESMTP id ED5EE108A54; Thu, 10 Sep 2015 00:15:24 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at vm1.sequanux.org Received: from vm1.sequanux.org ([127.0.0.1]) by localhost (vm1.sequanux.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id mS6B_eYGq-pZ; Thu, 10 Sep 2015 00:15:23 +0200 (CEST) Received: from localhost (unknown [78.250.153.233]) by vm1.sequanux.org (Postfix) with ESMTPSA id ACAEA108A44; Thu, 10 Sep 2015 00:15:21 +0200 (CEST) From: Simon Guinot To: Alan Cox , Jesse Barnes , Giel van Schijndel Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Pelletier , Vincent Donnefort , Yoann Sculo Subject: [PATCH] kernel/resource.c: fix muxed resource handling in __request_region() Date: Thu, 10 Sep 2015 00:15:18 +0200 Message-Id: <1441836918-24159-1-git-send-email-simon.guinot@sequanux.org> X-Mailer: git-send-email 2.1.4 In-Reply-To: <20150909220140.GD9892@kw.sim.vm.gnt> References: <20150909220140.GD9892@kw.sim.vm.gnt> Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org In __request_region, if a conflict with a BUSY and MUXED resource is detected, then the caller goes to sleep and waits for the resource to be released. A pointer on the conflicting resource is kept. At wake-up this pointer is used as a parent to retry to request the region. A first problem is that this pointer might well be invalid (if for example the conflicting resource have already been freed). An another problem is that the next call to __request_region() fails to detect a remaining conflict. The previously conflicting resource is passed as a parameter and __request_region() will look for a conflict among the children of this resource and not at the resource itself. It is likely to succeed anyway, even if there is still a conflict. Instead, the parent of the conflicting resource should be passed to __request_region(). As a fix attempt, this patch don't update the parent resource pointer in the case we have to wait for a muxed region right after. Reported-by: Vincent Pelletier Signed-off-by: Simon Guinot Tested-by: Vincent Donnefort Tested-by: Vincent Pelletier --- kernel/resource.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/resource.c b/kernel/resource.c index fed052a1bc9f..b8c84804db6a 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1072,9 +1072,10 @@ struct resource * __request_region(struct resource *parent, if (!conflict) break; if (conflict != parent) { - parent = conflict; - if (!(conflict->flags & IORESOURCE_BUSY)) + if (!(conflict->flags & IORESOURCE_BUSY)) { + parent = conflict; continue; + } } if (conflict->flags & flags & IORESOURCE_MUXED) { add_wait_queue(&muxed_resource_wait, &wait);