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>

1 files changed, 74 insertions, 43 deletions

diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
index 1d586d4f7b5..9b166d70ae9 100644
--- 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);