From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:35388 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752071Ab2LCTsK (ORCPT ); Mon, 3 Dec 2012 14:48:10 -0500 Message-ID: <1354564084.1809.390.camel@bling.home> Subject: Re: [PATCH] PCI AER: pci_get_domain_bus_and_slot() call missing required pci_dev_put() From: Alex Williamson To: Shuah Khan Cc: Betty Dall , bhelgaas@google.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, wangyijing@huawei.com, jiang.liu@huawei.com Date: Mon, 03 Dec 2012 12:48:04 -0700 In-Reply-To: References: <1354552622-687-1-git-send-email-betty.dall@hp.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: On Mon, 2012-12-03 at 10:40 -0700, Shuah Khan wrote: > On Mon, Dec 3, 2012 at 9:37 AM, Betty Dall wrote: > > The function aer_recover_queue() makes a call to pci_get_domain_bus_and_slot(). > > That function is documented to require that the caller decrement the > > reference count by calling pci_dev_put(). This patch adds the missing > > call to pci_dev_put(). > > > > Signed-off-by: Betty Dall > > --- > > drivers/pci/pcie/aer/aerdrv_core.c | 1 + > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c > > index af4e31c..43caf53 100644 > > --- a/drivers/pci/pcie/aer/aerdrv_core.c > > +++ b/drivers/pci/pcie/aer/aerdrv_core.c > > @@ -616,6 +616,7 @@ static void aer_recover_work_func(struct work_struct *work) > > continue; > > } > > do_recovery(pdev, entry.severity); > > + pci_dev_put(pdev); > > Are you sure pci_get_domain_bus_and_slot() does indeed increment the > reference count? I see that in the comments right above the > definition. > > pci_dev_get() does that for sure. I see a call trace of > > pci_dev_get() -> get_device() -> kobj_to_dev(kobject_get(&dev->kobj) etc. > > and kref_get() finally incrementing the > > static inline void kref_get(struct kref *kref) > { > WARN_ON(!atomic_read(&kref->refcount)); > atomic_inc(&kref->refcount); > } > > However, I could not find any evidence that > pci_get_domain_bus_and_slot() does that. I see > pci_get_domain_bus_and_slot() calling pci_domain_nr() and there are > several architecture specific defines for pci_domain_nr(). It is not > clear to me where does refcount get incremented from > pci_get_domain_bus_and_slot() is called. > > What am I missing? Trace back the for_each_pci_dev() for_each_pci_dev -> pci_get_device -> pci_get_subsys -> pci_get_dev_by_id -> bus_find_device -> get_device() The real question is how many places do we call for_each_pci_dev() without a put. It seems like pci_get_domain_bus_and_slot() doesn't even get it right since it should include a put of the non-matched devices. Thanks, Alex