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SubjectRe: [PATCH 1/2] PCI: Use local parameter pci_device_id for pci_get_subsys/class()
On Sat, 8 Sep 2012 21:42:20 +0800
Fengguang Wu <fengguang.wu@intel.com> wrote:

> On Fri, Sep 07, 2012 at 06:32:48PM -0700, Yinghai Lu wrote:
>
> > > 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.
>
> This makes lspci work again on my side. The caveat is, kzalloc() will
> zero out all data while the new local variable leaves some data
> uninitialized.

Yes, thanks for the quick root cause and fix to the bug in my code.

- Feng




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