powerpc/eeh: Introduce global mutex

The patch introduces global mutex for EEH so that the core data
structures can be protected by that. Also, 2 inline functions
are exported for that: eeh_lock() and eeh_unlock().
Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/eeh.h

@@ -146,6 +146,17 @@ struct eeh_ops {
 
 extern struct eeh_ops *eeh_ops;
 extern int eeh_subsystem_enabled;
+extern struct mutex eeh_mutex;
+
+static inline void eeh_lock(void)
+{
+	mutex_lock(&eeh_mutex);
+}
+
+static inline void eeh_unlock(void)
+{
+	mutex_unlock(&eeh_mutex);
+}
 
 /*
  * Max number of EEH freezes allowed before we consider the device
@@ -206,6 +217,10 @@ static inline void eeh_add_device_tree_early(struct device_node *dn) { }
 static inline void eeh_add_device_tree_late(struct pci_bus *bus) { }
 
 static inline void eeh_remove_bus_device(struct pci_dev *dev) { }
+
+static inline void eeh_lock(void) { }
+static inline void eeh_unlock(void) { }
+
 #define EEH_POSSIBLE_ERROR(val, type) (0)
 #define EEH_IO_ERROR_VALUE(size) (-1UL)
 #endif /* CONFIG_EEH */

arch/powerpc/platforms/pseries/eeh.c

@@ -92,6 +92,9 @@ struct eeh_ops *eeh_ops = NULL;
 int eeh_subsystem_enabled;
 EXPORT_SYMBOL(eeh_subsystem_enabled);
 
+/* Global EEH mutex */
+DEFINE_MUTEX(eeh_mutex);
+
 /* Lock to avoid races due to multiple reports of an error */
 static DEFINE_RAW_SPINLOCK(confirm_error_lock);