From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-it0-f45.google.com ([209.85.214.45]:56332 "EHLO mail-it0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751268AbdINRo2 (ORCPT ); Thu, 14 Sep 2017 13:44:28 -0400 Received: by mail-it0-f45.google.com with SMTP id g18so1060887itg.5 for ; Thu, 14 Sep 2017 10:44:28 -0700 (PDT) Subject: Re: iwlwifi firmware load broken in current -git From: Jens Axboe To: Srinath Mannam Cc: Bjorn Helgaas , Johannes Berg , Luca Coelho , "Grumbach, Emmanuel" , linuxwifi , "linux-wireless@vger.kernel.org" , "linux-pci@vger.kernel.org" References: <04c9b578-693c-1dc6-9f0f-904580231b21@kernel.dk> <1505232673.5400.243.camel@intel.com> <1505234187.5400.249.camel@coelho.fi> <4bcbcbc1-7c79-09f0-5071-bc2f53bf6574@kernel.dk> <1505246657.1974.11.camel@sipsolutions.net> <8de8d1e2-1673-e1ff-d0ac-6d3bb03e9e99@kernel.dk> Message-ID: <93bfbc9b-8829-66fa-f4d6-6d47124e460c@kernel.dk> (sfid-20170914_194431_951087_A23F5749) Date: Thu, 14 Sep 2017 11:44:25 -0600 MIME-Version: 1.0 In-Reply-To: <8de8d1e2-1673-e1ff-d0ac-6d3bb03e9e99@kernel.dk> Content-Type: text/plain; charset=utf-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 09/14/2017 11:35 AM, Jens Axboe wrote: > On 09/14/2017 11:28 AM, Srinath Mannam wrote: >> Hi Bjorn, >> >> On Thu, Sep 14, 2017 at 10:52 PM, Jens Axboe wrote: >>> >>> On 09/14/2017 11:11 AM, Bjorn Helgaas wrote: >>>> [+cc linux-pci] >>>> >>>> On Thu, Sep 14, 2017 at 12:00 PM, Jens Axboe wrote: >>>>> On 09/12/2017 02:04 PM, Johannes Berg wrote: >>>>>> On Tue, 2017-09-12 at 13:43 -0600, Jens Axboe wrote: >>>>>> >>>>>>> CC'ing the guilty part and Bjorn. I'm assuming it's the >>>>>>> pci_is_enabled() check, since the rest of the patch shouldn't have >>>>>>> functional changes. >>>>>> >>>>>> and pci_enable_bridge() already checks if it's already enabled, but >>>>>> still enables mastering in that case if it isn't: >>>>>> >>>>>> static void pci_enable_bridge(struct pci_dev *dev) >>>>>> { >>>>>> [...] >>>>>> if (pci_is_enabled(dev)) { >>>>>> if (!dev->is_busmaster) >>>>>> pci_set_master(dev); >>>>>> return; >>>>>> } >>>>>> >>>>>> so I guess due to the new check we end up with mastering disabled, and >>>>>> thus the firmware can't load since that's a DMA thing? >>>>> >>>>> Bjorn/Srinath, any input here? This is a regression that prevents wifi >>>>> from working on a pretty standard laptop. It'd suck to have this be in >>>>> -rc1. Seems like the trivial fix would be: >>>>> >>>>> >>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >>>>> index b0002daa50f3..ffbe11dbdd61 100644 >>>>> --- a/drivers/pci/pci.c >>>>> +++ b/drivers/pci/pci.c >>>>> @@ -1394,7 +1394,7 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) >>>>> return 0; /* already enabled */ >>>>> >>>>> bridge = pci_upstream_bridge(dev); >>>>> - if (bridge && !pci_is_enabled(bridge)) >>>>> + if (bridge) >> With this change and keeping "mutex_lock(&pci_bridge_mutex);" in >> pci_enable_bridge functoin will causes a nexted lock. > > Took a look, and looks like you are right. That code looks like a mess, > fwiw. > > I'd strongly suggest that the bad commit is reverted until a proper > solution is found, since the simple one-liner could potentially > introduce a deadlock with your patch applied. BTW, your patch looks pretty bad too, introducing a random mutex deep on code that can be recursive. Why isn't this check in pci_enable_device_flags() enough to prevent double-enable of an upstream bridge? if (atomic_inc_return(&dev->enable_cnt) > 1) return 0; /* already enabled */ -- Jens Axboe