From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Barnes Subject: Re: [PATCH] kernel/resource.c: fix muxed resource handling in __request_region() Date: Fri, 19 Feb 2016 15:25:13 -0800 Message-ID: <56C7A459.1090801@virtuousgeek.org> References: <20150909220140.GD9892@kw.sim.vm.gnt> <1441836918-24159-1-git-send-email-simon.guinot@sequanux.org> <20160219221056.23487da2@x2> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pa0-f44.google.com ([209.85.220.44]:34584 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1428550AbcBSXY5 (ORCPT ); Fri, 19 Feb 2016 18:24:57 -0500 In-Reply-To: <20160219221056.23487da2@x2> Sender: linux-gpio-owner@vger.kernel.org List-Id: linux-gpio@vger.kernel.org To: Vincent Pelletier , Simon Guinot Cc: Alan Cox , Giel van Schijndel , linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Donnefort , Yoann Sculo , Linus Torvalds +Linus (the de-facto resource guy). On 02/19/2016 01:10 PM, Vincent Pelletier wrote: > Hello, > > I finally got around to rebasing some patches, and realised that the > patch from Simon Guinot below still gets rebased over torvalds' v4.4 . > > Any reason it was not applied ? > Or was the issue fixed in another, non-git-conflicting way ? (I see > nothing recent in git log kernel/resource.c) > > I do not find a trace of a mail confirming that I tested it and that it > fixes the issue. So here goes: > Tested-by: Vincent Pelletier > > Testing details: bug reproduced on 4.1, patch applied over 4.1 and bug > disappeared. After rebasing this patch (along with others) over 4.4, > bug does not reappear. I did not try to reproduce bug with 4.4, but if > preferred I can give it a go. > > On Thu, 10 Sep 2015 00:15:18 +0200, Simon Guinot > wrote: >> 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); > > Regards, >