USB host: Fix lockdep warning in AMD PLL quirk

Booting latest kernel on my test machine produces a lockdep
warning from the usb_amd_find_chipset_info() function:

 WARNING: at /data/lemmy/linux.trees.git/kernel/lockdep.c:2465 lockdep_trace_alloc+0x95/0xc2()
 Hardware name: Snook
 Modules linked in:
 Pid: 959, comm: work_for_cpu Not tainted 2.6.39-rc2+ #22
 Call Trace:
  [<ffffffff8103c0d4>] warn_slowpath_common+0x80/0x98
  [<ffffffff812387e6>] ? T.492+0x24/0x26
  [<ffffffff8103c101>] warn_slowpath_null+0x15/0x17
  [<ffffffff81068667>] lockdep_trace_alloc+0x95/0xc2
  [<ffffffff810ed9ac>] slab_pre_alloc_hook+0x18/0x3b
  [<ffffffff810ef227>] kmem_cache_alloc_trace+0x25/0xba
  [<ffffffff812387e6>] T.492+0x24/0x26
  [<ffffffff81238816>] pci_get_subsys+0x2e/0x73
  [<ffffffff8123886c>] pci_get_device+0x11/0x13
  [<ffffffff814082a9>] usb_amd_find_chipset_info+0x3f/0x18a
...

It turns out that this function calls pci_get_device under a spin_lock
with irqs disabled, but the pci_get_device function is only allowed in
preemptible context.

This patch fixes the warning by making all data-structure
modifications on temporal storage and commiting this back
into the visible structure at the end. While at it, this
patch also moves the pci_dev_put calls out of the spinlocks
because this function might sleep too.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
index 1d586d4..9b166d7 100644 (file)
--- a/drivers/usb/host/pci-quirks.c
+++ b/drivers/usb/host/pci-quirks.c
@@ -84,65 +84,92 @@ int usb_amd_find_chipset_info(void)
 {
        u8 rev = 0;
        unsigned long flags;
+       struct amd_chipset_info info;
+       int ret;
 
        spin_lock_irqsave(&amd_lock, flags);
 
-       amd_chipset.probe_count++;
        /* probe only once */
-       if (amd_chipset.probe_count > 1) {
+       if (amd_chipset.probe_count > 0) {
+               amd_chipset.probe_count++;
                spin_unlock_irqrestore(&amd_lock, flags);
                return amd_chipset.probe_result;
        }
+       memset(&info, 0, sizeof(info));
+       spin_unlock_irqrestore(&amd_lock, flags);
 
-       amd_chipset.smbus_dev = pci_get_device(PCI_VENDOR_ID_ATI, 0x4385, NULL);
-       if (amd_chipset.smbus_dev) {
-               rev = amd_chipset.smbus_dev->revision;
+       info.smbus_dev = pci_get_device(PCI_VENDOR_ID_ATI, 0x4385, NULL);
+       if (info.smbus_dev) {
+               rev = info.smbus_dev->revision;
                if (rev >= 0x40)
-                       amd_chipset.sb_type = 1;
+                       info.sb_type = 1;
                else if (rev >= 0x30 && rev <= 0x3b)
-                       amd_chipset.sb_type = 3;
+                       info.sb_type = 3;
        } else {
-               amd_chipset.smbus_dev = pci_get_device(PCI_VENDOR_ID_AMD,
-                                                       0x780b, NULL);
-               if (!amd_chipset.smbus_dev) {
-                       spin_unlock_irqrestore(&amd_lock, flags);
-                       return 0;
+               info.smbus_dev = pci_get_device(PCI_VENDOR_ID_AMD,
+                                               0x780b, NULL);
+               if (!info.smbus_dev) {
+                       ret = 0;
+                       goto commit;
                }
-               rev = amd_chipset.smbus_dev->revision;
+
+               rev = info.smbus_dev->revision;
                if (rev >= 0x11 && rev <= 0x18)
-                       amd_chipset.sb_type = 2;
+                       info.sb_type = 2;
        }
 
-       if (amd_chipset.sb_type == 0) {
-               if (amd_chipset.smbus_dev) {
-                       pci_dev_put(amd_chipset.smbus_dev);
-                       amd_chipset.smbus_dev = NULL;
+       if (info.sb_type == 0) {
+               if (info.smbus_dev) {
+                       pci_dev_put(info.smbus_dev);
+                       info.smbus_dev = NULL;
                }
-               spin_unlock_irqrestore(&amd_lock, flags);
-               return 0;
+               ret = 0;
+               goto commit;
        }
 
-       amd_chipset.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD, 0x9601, NULL);
-       if (amd_chipset.nb_dev) {
-               amd_chipset.nb_type = 1;
+       info.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD, 0x9601, NULL);
+       if (info.nb_dev) {
+               info.nb_type = 1;
        } else {
-               amd_chipset.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD,
-                                                       0x1510, NULL);
-               if (amd_chipset.nb_dev) {
-                       amd_chipset.nb_type = 2;
-               } else  {
-                       amd_chipset.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD,
-                                                               0x9600, NULL);
-                       if (amd_chipset.nb_dev)
-                               amd_chipset.nb_type = 3;
+               info.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD, 0x1510, NULL);
+               if (info.nb_dev) {
+                       info.nb_type = 2;
+               } else {
+                       info.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD,
+                                                    0x9600, NULL);
+                       if (info.nb_dev)
+                               info.nb_type = 3;
                }
        }
 
-       amd_chipset.probe_result = 1;
+       ret = info.probe_result = 1;
        printk(KERN_DEBUG "QUIRK: Enable AMD PLL fix\n");
 
-       spin_unlock_irqrestore(&amd_lock, flags);
-       return amd_chipset.probe_result;
+commit:
+
+       spin_lock_irqsave(&amd_lock, flags);
+       if (amd_chipset.probe_count > 0) {
+               /* race - someone else was faster - drop devices */
+
+               /* Mark that we where here */
+               amd_chipset.probe_count++;
+               ret = amd_chipset.probe_result;
+
+               spin_unlock_irqrestore(&amd_lock, flags);
+
+               if (info.nb_dev)
+                       pci_dev_put(info.nb_dev);
+               if (info.smbus_dev)
+                       pci_dev_put(info.smbus_dev);
+
+       } else {
+               /* no race - commit the result */
+               info.probe_count++;
+               amd_chipset = info;
+               spin_unlock_irqrestore(&amd_lock, flags);
+       }
+
+       return ret;
 }
 EXPORT_SYMBOL_GPL(usb_amd_find_chipset_info);
 
@@ -284,6 +311,7 @@ EXPORT_SYMBOL_GPL(usb_amd_quirk_pll_enable);
 
 void usb_amd_dev_put(void)
 {
+       struct pci_dev *nb, *smbus;
        unsigned long flags;
 
        spin_lock_irqsave(&amd_lock, flags);
@@ -294,20 +322,23 @@ void usb_amd_dev_put(void)
                return;
        }
 
-       if (amd_chipset.nb_dev) {
-               pci_dev_put(amd_chipset.nb_dev);
-               amd_chipset.nb_dev = NULL;
-       }
-       if (amd_chipset.smbus_dev) {
-               pci_dev_put(amd_chipset.smbus_dev);
-               amd_chipset.smbus_dev = NULL;
-       }
+       /* save them to pci_dev_put outside of spinlock */
+       nb    = amd_chipset.nb_dev;
+       smbus = amd_chipset.smbus_dev;
+
+       amd_chipset.nb_dev = NULL;
+       amd_chipset.smbus_dev = NULL;
        amd_chipset.nb_type = 0;
        amd_chipset.sb_type = 0;
        amd_chipset.isoc_reqs = 0;
        amd_chipset.probe_result = 0;
 
        spin_unlock_irqrestore(&amd_lock, flags);
+
+       if (nb)
+               pci_dev_put(nb);
+       if (smbus)
+               pci_dev_put(smbus);
 }
 EXPORT_SYMBOL_GPL(usb_amd_dev_put);