Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752634AbaG1NHG (ORCPT ); Mon, 28 Jul 2014 09:07:06 -0400 Received: from smtp.citrix.com ([66.165.176.89]:47253 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751686AbaG1NHB (ORCPT ); Mon, 28 Jul 2014 09:07:01 -0400 X-IronPort-AV: E=Sophos;i="5.01,749,1400025600"; d="scan'208";a="156359550" Message-ID: <53D64AF3.4080202@citrix.com> Date: Mon, 28 Jul 2014 14:06:59 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Icedove/24.5.0 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk , , , , CC: Subject: Re: [PATCH v5 2/6] xen/pciback: Don't deadlock when unbinding. References: <1405354736-7358-1-git-send-email-konrad.wilk@oracle.com> <1405354736-7358-3-git-send-email-konrad.wilk@oracle.com> In-Reply-To: <1405354736-7358-3-git-send-email-konrad.wilk@oracle.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.2.76] X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/07/14 17:18, Konrad Rzeszutek Wilk wrote: > As commit 0a9fd0152929db372ff61b0d6c280fdd34ae8bdb > 'xen/pciback: Document the entry points for 'pcistub_put_pci_dev'' > explained there are four entry points in this function. > Two of them are when the user fiddles in the SysFS to > unbind a device which might be in use by a guest or not. > > Both 'unbind' states will cause a deadlock as the the PCI lock has > already been taken, which then pci_device_reset tries to take. > > We can simplify this by requiring that all callers of > pcistub_put_pci_dev MUST hold the device lock. And then > we can just call the lockless version of pci_device_reset. > > To make it even simpler we will modify xen_pcibk_release_pci_dev > to quality whether it should take a lock or not - as it ends > up calling xen_pcibk_release_pci_dev and needs to hold the lock. > > CC: stable@vger.kernel.org This deadlock is for a rather specific and uncommon use case (manually unbinding a PCI while it is passed-through). Is this critical enough to warrant a stable backport? > Reviewed-by: Boris Ostrovsky > Signed-off-by: Konrad Rzeszutek Wilk Reviewed-by: David Vrabel David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/