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

[Fengguang Wu <fengguang.wu@intel.com>]

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.

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 78a08b1..9148b6e 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -245,7 +245,12 @@ 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_device_id id;
+	struct pci_device_id id = {
+		.vendor = vendor,
+		.device = device,
+		.subvendor = ss_vendor,
+		.subdevice = ss_device,
+	};
 
 	/*
 	 * pci_find_subsys() can be called on the ide_setup() path,
@@ -256,11 +261,6 @@ struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
 	if (unlikely(no_pci_devices()))
 		return NULL;
 
-	id.vendor = vendor;
-	id.device = device;
-	id.subvendor = ss_vendor;
-	id.subdevice = ss_device;
-
 	return pci_get_dev_by_id(&id, from);
 }
 
@@ -300,11 +300,14 @@ 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_device_id id;
-
-	id.vendor = id.device = id.subvendor = id.subdevice = PCI_ANY_ID;
-	id.class_mask = PCI_ANY_ID;
-	id.class = class;
+	struct pci_device_id id = {
+		.vendor = PCI_ANY_ID,
+		.device = PCI_ANY_ID,
+		.subvendor = PCI_ANY_ID,
+		.subdevice = PCI_ANY_ID,
+		.class_mask = PCI_ANY_ID,
+		.class = class,
+	};
 
 	return pci_get_dev_by_id(&id, from);
 }