From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com ([192.55.52.93]:64987 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751214Ab2IMB30 (ORCPT ); Wed, 12 Sep 2012 21:29:26 -0400 Message-ID: <1347499761.30040.138.camel@yhuang-dev> Subject: Re: [PATCH v2 4/4] PCI/AER: fix a small race condition window when rmmod aer_inject From: Huang Ying To: Yijing Wang Cc: Bjorn Helgaas , Chen Gong , jiang.liu@huawei.com, Hanjun Guo , linux-pci@vger.kernel.org Date: Thu, 13 Sep 2012 09:29:21 +0800 In-Reply-To: <1347453225-7704-4-git-send-email-wangyijing@huawei.com> References: <1347453225-7704-1-git-send-email-wangyijing@huawei.com> <1347453225-7704-4-git-send-email-wangyijing@huawei.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: On Wed, 2012-09-12 at 20:33 +0800, Yijing Wang wrote: > Fix a small race condition window between pci_bus_ops_pop() and > pci_bus_set_ops() functions. > > Signed-off-by: Yijing Wang > Signed-off-by: Jiang Liu > --- > drivers/pci/pcie/aer/aer_inject.c | 8 ++------ > 1 files changed, 2 insertions(+), 6 deletions(-) > > diff --git a/drivers/pci/pcie/aer/aer_inject.c b/drivers/pci/pcie/aer/aer_inject.c > index bd043db..69c2d77 100644 > --- a/drivers/pci/pcie/aer/aer_inject.c > +++ b/drivers/pci/pcie/aer/aer_inject.c > @@ -141,12 +141,11 @@ static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus) > return NULL; > } > > +/* inject_lock must be held before calling */ > static struct pci_bus_ops *pci_bus_ops_pop(void) > { > - unsigned long flags; > struct pci_bus_ops *bus_ops = NULL; > > - spin_lock_irqsave(&inject_lock, flags); > if (list_empty(&pci_bus_ops_list)) > bus_ops = NULL; > else { > @@ -154,7 +153,6 @@ static struct pci_bus_ops *pci_bus_ops_pop(void) > list_del(lh); > bus_ops = list_entry(lh, struct pci_bus_ops, list); > } > - spin_unlock_irqrestore(&inject_lock, flags); > return bus_ops; > } > > @@ -610,14 +608,12 @@ static void __exit aer_inject_exit(void) > bus_unregister_notifier(&pci_bus_type, &aerinj_hp_notifier); > misc_deregister(&aer_inject_device); > > + spin_lock_irqsave(&inject_lock, flags); > while ((bus_ops = pci_bus_ops_pop())) { > pci_bus_set_ops(bus_ops->bus, bus_ops->ops); > kfree(bus_ops); > } > > - clean_untracked_pci_aer_ops(); > - > - spin_lock_irqsave(&inject_lock, flags); > list_for_each_entry_safe(err, err_next, &einjected, list) { > list_del(&err->list); > kfree(err); This may trigger a AB BA dead lock. In aer_inject_exit, the lock sequence is: inject_lock -> pci_lock In pci config read/write path, the lock sequence is: pci_lock -> inject_lock With lockdep enabled, you may found warning on that. Best Regards, Huang YIng