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    SubjectRe: pci_get_subsys: GFP_KERNEL allocations with IRQs disabled
    Hi Bjorn,

    On Wed, 22 Aug 2012 11:02:52 -0700
    Bjorn Helgaas <bhelgaas@google.com> wrote:

    > On Wed, Aug 22, 2012 at 12:49 AM, Feng Tang <feng.tang@intel.com> wrote:
    > > Hi Fengguang,
    > >
    > >
    > > On Wed, 22 Aug 2012 10:50:08 +0800
    > > Fengguang Wu <fengguang.wu@intel.com> wrote:
    > >
    > >> Feng,
    > >>
    > >> > I think it's pci_get_subsys() triggered this assert:
    > >> >
    > >> > /*
    > >> > * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
    > >> > */
    > >> > if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
    > >> > return;
    > >>
    > >> It's bisected down to this commit:
    > >>
    > >> commit 55c844a4dd16a4d1fdc0cf2a283ec631a02ec448
    > >> Author: Feng Tang <feng.tang@intel.com>
    > >> AuthorDate: Wed May 30 23:15:41 2012 +0800
    > >> Commit: Ingo Molnar <mingo@kernel.org>
    > >> CommitDate: Wed Jun 6 12:03:23 2012 +0200
    > >>
    > >> x86/reboot: Fix a warning message triggered by stop_other_cpus()
    > >>
    > >> Thanks,
    > >> Fengguang
    > >
    > > Thanks for the bisection.
    > >
    > > Revert my commit should be a solution, but can we simply make the pci_device_id
    > > a local on stack one instead of using sleepable kmalloc for it, as this
    > > sounds fragile when pci_get_subsys get called in a late system reboot stage?
    >
    > I think this is a great idea. Can you make this a real patch, with a
    > changelog and Signed-off-by?

    Thanks and will do.

    >
    > We should also remove the obsolete comment about early boot. I'm not
    > sure the no_pci_devices() check is needed, either. And we can make
    > the same simplification in pci_get_class().

    Will check the no_pci_devices() part, and try to make it a separate
    patch for easy reverting in case of error.

    >
    > > ------------
    > > diff --git a/drivers/pci/search.c b/drivers/pci/search.c
    > > index 993d4a0..e5ccede 100644
    > > --- a/drivers/pci/search.c
    > > +++ b/drivers/pci/search.c
    > > @@ -246,7 +246,7 @@ struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
    > > struct pci_dev *from)
    > > {
    > > + id.vendor = vendor;
    > > + id.device = device;
    > > + id.subvendor = ss_vendor;
    > > + id.subdevice = ss_device;
    > >
    > > + pdev = pci_get_dev_by_id(&id, from);
    >
    > No need for "pdev" here, since we don't have to free anything.

    ok, will directly return it.

    Thanks,
    Feng


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