[PATCH v4 02/15] PCI Hotplug: serialize pci_hp_register/deregister

[Alex Chiang <achiang@hp.com>]

Add explicit locking to pci_hp_register/deregister. For a given pci_slot,
we want to make sure that the pci_slot->hotplug pointer isn't being
changed from underneath us.

Cc: jbarnes@virtuousgeek.org
Cc: kristen.c.accardi@intel.com
Cc: matthew@wil.cx
Cc: kaneshige.kenji@jp.fujitsu.com
Signed-off-by: Alex Chiang <achiang@hp.com>
---

 drivers/pci/hotplug/pci_hotplug_core.c |    7 +++++++
 drivers/pci/slot.c                     |    4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/hotplug/pci_hotplug_core.c b/drivers/pci/hotplug/pci_hotplug_core.c
index 0e7a511..e00266b 100644
--- a/drivers/pci/hotplug/pci_hotplug_core.c
+++ b/drivers/pci/hotplug/pci_hotplug_core.c
@@ -37,6 +37,7 @@
 #include <linux/init.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
+#include <linux/mutex.h>
 #include <linux/pci.h>
 #include <linux/pci_hotplug.h>
 #include <asm/uaccess.h>
@@ -554,6 +555,7 @@ out:
  *
  * Returns 0 if successful, anything else for an error.
  */
+static DEFINE_MUTEX(pci_hp_mutex);
 int pci_hp_register(struct hotplug_slot *slot, struct pci_bus *bus, int slot_nr,
 			const char *name)
 {
@@ -583,7 +585,9 @@ int pci_hp_register(struct hotplug_slot *slot, struct pci_bus *bus, int slot_nr,
 	if (IS_ERR(pci_slot))
 		return PTR_ERR(pci_slot);
 
+	mutex_lock(&pci_hp_mutex);
 	if (pci_slot->hotplug) {
+		mutex_unlock(&pci_hp_mutex);
 		dbg("%s: already claimed\n", __func__);
 		pci_destroy_slot(pci_slot);
 		return -EBUSY;
@@ -591,6 +595,7 @@ int pci_hp_register(struct hotplug_slot *slot, struct pci_bus *bus, int slot_nr,
 
 	slot->pci_slot = pci_slot;
 	pci_slot->hotplug = slot;
+	mutex_unlock(&pci_hp_mutex);
 
 	/*
 	 * Allow pcihp drivers to override the ACPI_PCI_SLOT name.
@@ -635,6 +640,7 @@ int pci_hp_deregister(struct hotplug_slot *hotplug)
 	if (temp != hotplug)
 		return -ENODEV;
 
+	mutex_lock(&pci_hp_mutex);
 	spin_lock(&pci_hotplug_slot_list_lock);
 	list_del(&hotplug->slot_list);
 	spin_unlock(&pci_hotplug_slot_list_lock);
@@ -645,6 +651,7 @@ int pci_hp_deregister(struct hotplug_slot *hotplug)
 
 	hotplug->release(hotplug);
 	slot->hotplug = NULL;
+	mutex_unlock(&pci_hp_mutex);
 	pci_destroy_slot(slot);
 
 	return 0;
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index 0c6db03..1fffb27 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -164,10 +164,10 @@ placeholder:
 	pr_debug("%s: created pci_slot on %04x:%02x:%02x\n",
 		 __func__, pci_domain_nr(parent), parent->number, slot_nr);
 
- out:
+out:
 	up_write(&pci_bus_sem);
 	return slot;
- err:
+err:
 	kfree(slot);
 	slot = ERR_PTR(err);
 	goto out;