PCI: fix nested spinlock hang in aer_inject

The aer_inject module hangs in aer_inject() when checking the device's
error masks.  The hang is due to a recursive use of the aer_inject lock.
The aer_inject() routine grabs the lock while processing the error and then
calls pci_read_config_dword to read the masks. The pci_read_config_dword
routine is earlier overridden by pci_read_aer, which among other things,
grabs the aer_inject lock.

Fixed by moving the pci_read_config_dword calls to read the masks to before
the lock is taken.

Acked-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pcie/aer/aer_inject.c

@@ -321,7 +321,7 @@ static int aer_inject(struct aer_error_inj *einj)
 	unsigned long flags;
 	unsigned int devfn = PCI_DEVFN(einj->dev, einj->fn);
 	int pos_cap_err, rp_pos_cap_err;
-	u32 sever, mask;
+	u32 sever, cor_mask, uncor_mask;
 	int ret = 0;
 
 	dev = pci_get_domain_bus_and_slot((int)einj->domain, einj->bus, devfn);
@@ -339,6 +339,9 @@ static int aer_inject(struct aer_error_inj *einj)
 		goto out_put;
 	}
 	pci_read_config_dword(dev, pos_cap_err + PCI_ERR_UNCOR_SEVER, &sever);
+	pci_read_config_dword(dev, pos_cap_err + PCI_ERR_COR_MASK, &cor_mask);
+	pci_read_config_dword(dev, pos_cap_err + PCI_ERR_UNCOR_MASK,
+			      &uncor_mask);
 
 	rp_pos_cap_err = pci_find_ext_capability(rpdev, PCI_EXT_CAP_ID_ERR);
 	if (!rp_pos_cap_err) {
@@ -374,17 +377,14 @@ static int aer_inject(struct aer_error_inj *einj)
 	err->header_log2 = einj->header_log2;
 	err->header_log3 = einj->header_log3;
 
-	pci_read_config_dword(dev, pos_cap_err + PCI_ERR_COR_MASK, &mask);
-	if (einj->cor_status && !(einj->cor_status & ~mask)) {
+	if (einj->cor_status && !(einj->cor_status & ~cor_mask)) {
 		ret = -EINVAL;
 		printk(KERN_WARNING "The correctable error(s) is masked "
 				"by device\n");
 		spin_unlock_irqrestore(&inject_lock, flags);
 		goto out_put;
 	}
-
-	pci_read_config_dword(dev, pos_cap_err + PCI_ERR_UNCOR_MASK, &mask);
-	if (einj->uncor_status && !(einj->uncor_status & ~mask)) {
+	if (einj->uncor_status && !(einj->uncor_status & ~uncor_mask)) {
 		ret = -EINVAL;
 		printk(KERN_WARNING "The uncorrectable error(s) is masked "
 				"by device\n");