[PATCH] USB host: Fix lockdep warning in AMD PLL quirk

[Joerg Roedel]

Booting 2.6.38 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
 sr0: scsi3-mmc drive: 48x/48x writer dvd-ram cd/rw xa/form2 cdda tray
  [<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 this by using temporary variables in the quirk
algorithm and commiting them later to the struct under the lock. This
moves all pci_get_device() invocations out of the spin_lock and fixes
the lockdep warning.

Cc: stable@xxxxxxxxxx
Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
---
 drivers/usb/host/pci-quirks.c |   86 +++++++++++++++++++++++++----------------
 1 files changed, 52 insertions(+), 34 deletions(-)

diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
index 1d586d4..b5802f6 100644
--- a/drivers/usb/host/pci-quirks.c
+++ b/drivers/usb/host/pci-quirks.c
@@ -84,65 +84,83 @@ 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) {
 		spin_unlock_irqrestore(&amd_lock, flags);
 		return amd_chipset.probe_result;
 	}
+	info = amd_chipset;
+	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");
 
+commit:
+
+	spin_lock_irqsave(&amd_lock, flags);
+	if (amd_chipset.probe_count > 0) {
+		/* race - someone else was faster - drop devices */
+		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 amd_chipset.probe_result;
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(usb_amd_find_chipset_info);
 
-- 
1.7.1


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