From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Guinot 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> References: <20150909220140.GD9892@kw.sim.vm.gnt> Return-path: 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 In-Reply-To: <20150909220140.GD9892@kw.sim.vm.gnt> Sender: linux-gpio-owner@vger.kernel.org List-Id: linux-gpio@vger.kernel.org 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 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 --- 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); -- 2.1.4