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SubjectRe: [PATCH -v3 40/47] PCI: Add pci bus removal through /sys/.../pci_bus/.../remove
Hi Yinghai,
I found many other drivers assume that a pci bus won't disappear if
the corresponding PCI bridge device still exists. The sysfs interface proposed
here breaks that assumption and may cause many access-after-free issues.
So what's the purpose of this interface? Should we remove this interface or
enhance other drivers to avoid invalid memory access issues?
Thanks!
Gerry

On 03/19/2012 01:46 PM, Yinghai Lu wrote:
> it supports both pci root bus and pci bus under pci bridge.
>
> -v2: Change to three returns way in dev_bus_remove_store.
>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> Cc: Randy Dunlap <rdunlap@xenotime.net>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-doc@vger.kernel.org
> ---
> Documentation/ABI/testing/sysfs-bus-pci | 8 ++++++++
> drivers/pci/pci-sysfs.c | 30 ++++++++++++++++++++++++++++++
> 2 files changed, 38 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index 95f0f37..22392de 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -92,6 +92,14 @@ Description:
> hot-remove the PCI device and any of its children.
> Depends on CONFIG_HOTPLUG.
>
> +What: /sys/bus/pci/devices/.../pci_bus/.../remove
> +Date: March 2012
> +Contact: Linux PCI developers <linux-pci@vger.kernel.org>
> +Description:
> + Writing a non-zero value to this attribute will
> + hot-remove the PCI bus and any of its children.
> + Depends on CONFIG_HOTPLUG.
> +
> What: /sys/bus/pci/devices/.../pci_bus/.../rescan
> Date: May 2011
> Contact: Linux PCI developers <linux-pci@vger.kernel.org>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index d33a1bc..afba77b 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -391,6 +391,35 @@ remove_store(struct device *dev, struct device_attribute *dummy,
> return count;
> }
>
> +static void bus_remove_callback(struct device *dev)
> +{
> + struct pci_bus *bus = to_pci_bus(dev);
> +
> + mutex_lock(&pci_remove_rescan_mutex);
> + pci_stop_and_remove_bus(bus);
> + mutex_unlock(&pci_remove_rescan_mutex);
> +}
> +static ssize_t
> +dev_bus_remove_store(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + int err;
> + unsigned long val;
> +
> + if (kstrtoul(buf, 0, &val) < 0)
> + return -EINVAL;
> +
> + if (!val)
> + return count;
> +
> + err = device_schedule_callback(dev, bus_remove_callback);
> +
> + if (err)
> + return err;
> +
> + return count;
> +}
> +
> static void bus_rescan_callback(struct device *dev)
> {
> struct pci_bus *bus = to_pci_bus(dev);
> @@ -450,6 +479,7 @@ struct device_attribute pci_dev_attrs[] = {
> struct device_attribute pcibus_dev_attrs[] = {
> #ifdef CONFIG_HOTPLUG
> __ATTR(rescan, (S_IWUSR|S_IWGRP), NULL, dev_bus_rescan_store),
> + __ATTR(remove, (S_IWUSR|S_IWGRP), NULL, dev_bus_remove_store),
> #endif
> __ATTR(cpuaffinity, S_IRUGO, pci_bus_show_cpumaskaffinity, NULL),
> __ATTR(cpulistaffinity, S_IRUGO, pci_bus_show_cpulistaffinity, NULL),



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