1 files changed, 24 insertions, 0 deletions

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 45f2b20ef513..fab381ed853c 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -193,6 +193,18 @@ static struct pci_dev * pci_find_subsys(unsigned int vendor,
         struct pci_dev *dev;
 
         WARN_ON(in_interrupt());
+
+        /*
+         * pci_find_subsys() can be called on the ide_setup() path, super-early
+         * in boot.  But the down_read() will enable local interrupts, which
+         * can cause some machines to crash.  So here we detect and flag that
+         * situation and bail out early.
+         */
+        if (unlikely(list_empty(&pci_devices))) {
+                printk(KERN_INFO "pci_find_subsys() called while pci_devices "
+                                "is still empty\n");
+                return NULL;
+        }
         down_read(&pci_bus_sem);
         n = from ? from->global_list.next : pci_devices.next;
 
@@ -259,6 +271,18 @@ pci_get_subsys(unsigned int vendor, unsigned int device,
         struct pci_dev *dev;
 
         WARN_ON(in_interrupt());
+
+        /*
+         * pci_get_subsys() can potentially be called by drivers super-early
+         * in boot.  But the down_read() will enable local interrupts, which
+         * can cause some machines to crash.  So here we detect and flag that
+         * situation and bail out early.
+         */
+        if (unlikely(list_empty(&pci_devices))) {
+                printk(KERN_NOTICE "pci_get_subsys() called while pci_devices "
+                                "is still empty\n");
+                return NULL;
+        }
         down_read(&pci_bus_sem);
         n = from ? from->global_list.next : pci_devices.next;