Re: [PATCH 1/2] PCI: Use local parameter pci_device_id for pci_get_subsys/class()

[Yinghai Lu <yinghai@kernel.org>]

On Fri, Sep 7, 2012 at 6:00 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> On Thu, Aug 23, 2012 at 12:45 AM, Feng Tang <feng.tang@intel.com> wrote:
>> From 57a28ee5e7662ca28ba4c793aa037d64bd082dee Mon Sep 17 00:00:00 2001
>> From: Feng Tang <feng.tang@intel.com>
>> Date: Wed, 22 Aug 2012 15:41:51 +0800
>> Subject: [PATCH 1/2] PCI: Use local parameter pci_device_id for pci_get_subsys/class()
>>
>> This fixes a kernel warning https://lkml.org/lkml/2012/7/31/682
>>
>> pci_get_subsys() may get called in late system reboot stage, using
>> a sleepable kmalloc() sounds fragile and will casue a kernel warning
>> with my recent commmit 55c844a "x86/reboot: Fix a warning message
>> triggered by stop_other_cpus()" which disable local interrupt in
>> late system shutdown/reboot phase. Using a local parameter instead
>> will fix it and make it eligible for calling forom atomic context.
>>
>> Do the same change for the pci_get_class() as suggeted by Bjorn Helgaas
>>
>> Bisected-by: Fengguang Wu <fengguang.wu@intel.com>
>> Signed-off-by: Feng Tang <feng.tang@intel.com>
>> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com>
>> ---
>>  drivers/pci/search.c |   35 +++++++++++------------------------
>>  1 files changed, 11 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
>> index 993d4a0..78a08b1 100644
>> --- a/drivers/pci/search.c
>> +++ b/drivers/pci/search.c
>> @@ -245,8 +245,7 @@ struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
>>                                unsigned int ss_vendor, unsigned int ss_device,
>>                                struct pci_dev *from)
>>  {
>> -       struct pci_dev *pdev;
>> -       struct pci_device_id *id;
>> +       struct pci_device_id id;
>>
>>         /*
>>          * pci_find_subsys() can be called on the ide_setup() path,
>> @@ -257,18 +256,12 @@ struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
>>         if (unlikely(no_pci_devices()))
>>                 return NULL;
>>
>> -       id = kzalloc(sizeof(*id), GFP_KERNEL);
>> -       if (!id)
>> -               return NULL;
>> -       id->vendor = vendor;
>> -       id->device = device;
>> -       id->subvendor = ss_vendor;
>> -       id->subdevice = ss_device;
>> -
>> -       pdev = pci_get_dev_by_id(id, from);
>> -       kfree(id);
>> +       id.vendor = vendor;
>> +       id.device = device;
>> +       id.subvendor = ss_vendor;
>> +       id.subdevice = ss_device;
>>
>> -       return pdev;
>> +       return pci_get_dev_by_id(&id, from);
>>  }
>>
>>  /**
>> @@ -307,19 +300,13 @@ pci_get_device(unsigned int vendor, unsigned int device, struct pci_dev *from)
>>   */
>>  struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from)
>>  {
>> -       struct pci_dev *dev;
>> -       struct pci_device_id *id;
>> +       struct pci_device_id id;
>>
>> -       id = kzalloc(sizeof(*id), GFP_KERNEL);
>> -       if (!id)
>> -               return NULL;
>> -       id->vendor = id->device = id->subvendor = id->subdevice = PCI_ANY_ID;
>> -       id->class_mask = PCI_ANY_ID;
>> -       id->class = class;
>> +       id.vendor = id.device = id.subvendor = id.subdevice = PCI_ANY_ID;
>> +       id.class_mask = PCI_ANY_ID;
>> +       id.class = class;
>>
>> -       dev = pci_get_dev_by_id(id, from);
>> -       kfree(id);
>> -       return dev;
>> +       return pci_get_dev_by_id(&id, from);
>>  }
>>
>>  /**
>
> with this one in pci/next pci config in /sys are not created.
>
> 10:~ # lspci -tv
> pcilib: Cannot open /sys/bus/pci/devices/0000:00:03.0/config
> lspci: Unable to read the standard configuration space header of
> device 0000:00:03.0
> pcilib: Cannot open /sys/bus/pci/devices/0000:00:02.0/config
> lspci: Unable to read the standard configuration space header of
> device 0000:00:02.0
> pcilib: Cannot open /sys/bus/pci/devices/0000:00:01.3/config
> lspci: Unable to read the standard configuration space header of
> device 0000:00:01.3
> pcilib: Cannot open /sys/bus/pci/devices/0000:00:01.1/config
> lspci: Unable to read the standard configuration space header of
> device 0000:00:01.1
> pcilib: Cannot open /sys/bus/pci/devices/0000:00:01.0/config
> lspci: Unable to read the standard configuration space header of
> device 0000:00:01.0
> pcilib: Cannot open /sys/bus/pci/devices/0000:00:00.0/config
> lspci: Unable to read the standard configuration space header of
> device 0000:00:00.0
> -[0000:00]-
>
> bisected to this commit
>
> ccee7d23102f5e5765ec24779c5b77472af8f79e is the first bad commit
> commit ccee7d23102f5e5765ec24779c5b77472af8f79e
> Author: Feng Tang <feng.tang@intel.com>
> Date:   Thu Aug 23 15:45:03 2012 +0800
>
>     PCI: Use pci_device_id on stack for pci_get_subsys/class() to avoid kmalloc
>
>     This fixes a kernel warning https://lkml.org/lkml/2012/7/31/682
>
>     pci_get_subsys() may get called in late system reboot stage, using
>     a sleepable kmalloc() sounds fragile and will cause a kernel warning
>     with my recent commmit 55c844a "x86/reboot: Fix a warning message
>     triggered by stop_other_cpus()" which disable local interrupt in
>     late system shutdown/reboot phase. Using a local parameter instead
>     will fix it and make it eligible for calling forom atomic context.
>
>     Do the same change for the pci_get_class() as suggested by Bjorn Helgaas
>
>     [bhelgaas: changelog]
>     Bisected-by: Fengguang Wu <fengguang.wu@intel.com>
>     Signed-off-by: Feng Tang <feng.tang@intel.com>
>     Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>     Reviewed-by: Fengguang Wu <fengguang.wu@intel.com>
>
> :040000 040000 dee62a035816b73abc68e40de8f21c7349efc4cb
> 70b2a6258bffa1ab963bd650d8f5d02da774fbce M      drivers
>
> so the stack get overrun ?
>
> Bjorn, I think it is this one that cause lspci broken that I mentioned
> during meeting at San Diego.
>

Greg,

Any reason for using kmalloc instead of local variable during your
rewriting pci search code?

commit 95247b57ed844511a212265b45cf9a919753aea1
Author: Greg Kroah-Hartman <gregkh@suse.de>
Date:   Wed Feb 13 11:03:58 2008 -0800

    PCI: clean up search.c a lot

    This cleans up the search.c file, now using the pci list of devices that
    are created for the driver core, instead of relying on our separate list
    of devices.  It's better to use the functions already created for this
    kind of thing, instead of rolling our own all the time.

    This work is done in anticipation of getting rid of that second list of
    pci devices all together.

    And it ends up saving code, always a nice benefit.

    This also removes one compiler warning for when CONFIG_PCI_LEGACY is
    enabled as we no longer internally use the deprecated functions anymore.

    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>