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    SubjectRe: pci_get_subsys: GFP_KERNEL allocations with IRQs disabled
    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?

    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().

    > ------------
    > 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)
    > {
    > 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,
    > @@ -257,17 +257,12 @@ 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;
    >
    > + pdev = pci_get_dev_by_id(&id, from);

    No need for "pdev" here, since we don't have to free anything.

    > return pdev;
    > }


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