From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f174.google.com ([209.85.217.174]:43562 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752360Ab2IKWBA (ORCPT ); Tue, 11 Sep 2012 18:01:00 -0400 Received: by lbbgj3 with SMTP id gj3so712165lbb.19 for ; Tue, 11 Sep 2012 15:00:58 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1344355862-2726-2-git-send-email-jiang.liu@huawei.com> References: <1344355862-2726-1-git-send-email-jiang.liu@huawei.com> <1344355862-2726-2-git-send-email-jiang.liu@huawei.com> From: Bjorn Helgaas Date: Tue, 11 Sep 2012 16:00:38 -0600 Message-ID: Subject: Re: [RFC PATCH v1 01/22] PCI: use pci_get_domain_bus_and_slot() to avoid race conditions To: Jiang Liu Cc: Don Dutile , Yinghai Lu , Greg KH , Kenji Kaneshige , Jiang Liu , Taku Izumi , "Rafael J . Wysocki" , Yijing Wang , Xinwei Hu , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-pci-owner@vger.kernel.org List-ID: On Tue, Aug 7, 2012 at 10:10 AM, Jiang Liu wrote: > There's a typical usage pattern to search a PCI device under a specific > PCI bus (domian, busno) as below: > struct pci_bus *pci_bus = pci_find_bus(domain, busno); > struct pci_dev *pci_dev = pci_get_slot(pci_bus, devfn); > > The above code has a race window between pci_find_bus() and pci_get_slot() > if PCI hotplug operations happen between them which removes the pci_bus. > So use PCI hotplug safe interface pci_get_domain_bus_and_slot() instead, > which also reduces code complexity. This makes sense to me. If we support hotplug, it's fundamentally unsafe to keep a struct pci_bus * without having a reference or some way to make sure it doesn't go away. I think we should try to eradicate all uses of pci_find_bus() and pci_find_next_bus(). > Signed-off-by: Jiang Liu > --- > arch/ia64/sn/kernel/io_common.c | 4 +--- > drivers/gpu/vga/vgaarb.c | 15 +++------------ > drivers/pci/hotplug/cpcihp_generic.c | 8 ++------ > drivers/pci/iov.c | 8 ++------ > drivers/pci/xen-pcifront.c | 10 ++-------- > 5 files changed, 10 insertions(+), 35 deletions(-) > > diff --git a/arch/ia64/sn/kernel/io_common.c b/arch/ia64/sn/kernel/io_common.c > index fbb5f2f..8630875 100644 > --- a/arch/ia64/sn/kernel/io_common.c > +++ b/arch/ia64/sn/kernel/io_common.c > @@ -229,7 +229,6 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info, > { > int segment = pci_domain_nr(dev->bus); > struct pcibus_bussoft *bs; > - struct pci_bus *host_pci_bus; > struct pci_dev *host_pci_dev; > unsigned int bus_no, devfn; > > @@ -245,8 +244,7 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info, > > bus_no = (pcidev_info->pdi_slot_host_handle >> 32) & 0xff; > devfn = pcidev_info->pdi_slot_host_handle & 0xffffffff; > - host_pci_bus = pci_find_bus(segment, bus_no); > - host_pci_dev = pci_get_slot(host_pci_bus, devfn); > + host_pci_dev = pci_get_domain_bus_and_slot(segment, bus_no, devfn); > > pcidev_info->host_pci_dev = host_pci_dev; > pcidev_info->pdi_linux_pcidev = dev; > diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c > index 3df8fc0..b6852b7 100644 > --- a/drivers/gpu/vga/vgaarb.c > +++ b/drivers/gpu/vga/vgaarb.c > @@ -1066,7 +1066,6 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf, > } > > } else if (strncmp(curr_pos, "target ", 7) == 0) { > - struct pci_bus *pbus; > unsigned int domain, bus, devfn; > struct vga_device *vgadev; > > @@ -1085,19 +1084,11 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf, > pr_debug("vgaarb: %s ==> %x:%x:%x.%x\n", curr_pos, > domain, bus, PCI_SLOT(devfn), PCI_FUNC(devfn)); > > - pbus = pci_find_bus(domain, bus); > - pr_debug("vgaarb: pbus %p\n", pbus); > - if (pbus == NULL) { > - pr_err("vgaarb: invalid PCI domain and/or bus address %x:%x\n", > - domain, bus); > - ret_val = -ENODEV; > - goto done; > - } > - pdev = pci_get_slot(pbus, devfn); > + pdev = pci_get_domain_bus_and_slot(domain, bus, devfn); > pr_debug("vgaarb: pdev %p\n", pdev); > if (!pdev) { > - pr_err("vgaarb: invalid PCI address %x:%x\n", > - bus, devfn); > + pr_err("vgaarb: invalid PCI address %x:%x:%x\n", > + domain, bus, devfn); > ret_val = -ENODEV; > goto done; > } > diff --git a/drivers/pci/hotplug/cpcihp_generic.c b/drivers/pci/hotplug/cpcihp_generic.c > index 81af764..a6a71c4 100644 > --- a/drivers/pci/hotplug/cpcihp_generic.c > +++ b/drivers/pci/hotplug/cpcihp_generic.c > @@ -154,12 +154,8 @@ static int __init cpcihp_generic_init(void) > if(!r) > return -EBUSY; > > - bus = pci_find_bus(0, bridge_busnr); > - if (!bus) { > - err("Invalid bus number %d", bridge_busnr); > - return -EINVAL; > - } > - dev = pci_get_slot(bus, PCI_DEVFN(bridge_slot, 0)); > + dev = pci_get_domain_bus_and_slot(0, bridge_busnr, > + PCI_DEVFN(bridge_slot, 0)); > if(!dev || dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) { > err("Invalid bridge device %s", bridge); > pci_dev_put(dev); > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c > index 74bbaf8..c7d2969 100644 > --- a/drivers/pci/iov.c > +++ b/drivers/pci/iov.c > @@ -152,15 +152,11 @@ failed1: > static void virtfn_remove(struct pci_dev *dev, int id, int reset) > { > char buf[VIRTFN_ID_LEN]; > - struct pci_bus *bus; > struct pci_dev *virtfn; > struct pci_sriov *iov = dev->sriov; > > - bus = pci_find_bus(pci_domain_nr(dev->bus), virtfn_bus(dev, id)); > - if (!bus) > - return; > - > - virtfn = pci_get_slot(bus, virtfn_devfn(dev, id)); > + virtfn = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus), > + virtfn_bus(dev, id), virtfn_devfn(dev, id)); > if (!virtfn) > return; > > diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c > index d6cc62c..def8d0b 100644 > --- a/drivers/pci/xen-pcifront.c > +++ b/drivers/pci/xen-pcifront.c > @@ -982,7 +982,6 @@ static int pcifront_detach_devices(struct pcifront_device *pdev) > int err = 0; > int i, num_devs; > unsigned int domain, bus, slot, func; > - struct pci_bus *pci_bus; > struct pci_dev *pci_dev; > char str[64]; > > @@ -1032,13 +1031,8 @@ static int pcifront_detach_devices(struct pcifront_device *pdev) > goto out; > } > > - pci_bus = pci_find_bus(domain, bus); > - if (!pci_bus) { > - dev_dbg(&pdev->xdev->dev, "Cannot get bus %04x:%02x\n", > - domain, bus); > - continue; > - } > - pci_dev = pci_get_slot(pci_bus, PCI_DEVFN(slot, func)); > + pci_dev = pci_get_domain_bus_and_slot(domain, bus, > + PCI_DEVFN(slot, func)); > if (!pci_dev) { > dev_dbg(&pdev->xdev->dev, > "Cannot get PCI device %04x:%02x:%02x.%d\n", > -- > 1.7.9.5 >