ACPICA: Fix AcpiWalkNamespace race condition with table unload

Added a reader/writer locking mechanism to allow multiple
concurrent namespace walks (readers), but a dynamic table unload
will have exclusive access to the namespace. This fixes a problem
where a table unload could delete the portion of the namespace that
is currently being examined by a walk.  Adds a new file, utlock.c
that implements the reader/writer lock mechanism. ACPICA BZ 749.

http://www.acpica.org/bugzilla/show_bug.cgi?id=749

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 15 insertions, 8 deletions

diff --git a/drivers/acpi/acpica/utmutex.c b/drivers/acpi/acpica/utmutex.c
index 14eb52c4d64..26c93a748e6 100644
--- a/drivers/acpi/acpica/utmutex.c
+++ b/drivers/acpi/acpica/utmutex.c
@@ -60,7 +60,8 @@ static acpi_status acpi_ut_delete_mutex(acpi_mutex_handle mutex_id);
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Create the system mutex objects.
+ * DESCRIPTION: Create the system mutex objects. This includes mutexes,
+ *              spin locks, and reader/writer locks.
  *
  ******************************************************************************/
 
@@ -71,9 +72,8 @@ acpi_status acpi_ut_mutex_initialize(void)
 
 	ACPI_FUNCTION_TRACE(ut_mutex_initialize);
 
-	/*
-	 * Create each of the predefined mutex objects
-	 */
+	/* Create each of the predefined mutex objects */
+
 	for (i = 0; i < ACPI_NUM_MUTEX; i++) {
 		status = acpi_ut_create_mutex(i);
 		if (ACPI_FAILURE(status)) {
@@ -86,6 +86,9 @@ acpi_status acpi_ut_mutex_initialize(void)
 	spin_lock_init(acpi_gbl_gpe_lock);
 	spin_lock_init(acpi_gbl_hardware_lock);
 
+	/* Create the reader/writer lock for namespace access */
+
+	status = acpi_ut_create_rw_lock(&acpi_gbl_namespace_rw_lock);
 	return_ACPI_STATUS(status);
 }
 
@@ -97,7 +100,8 @@ acpi_status acpi_ut_mutex_initialize(void)
  *
  * RETURN:      None.
  *
- * DESCRIPTION: Delete all of the system mutex objects.
+ * DESCRIPTION: Delete all of the system mutex objects. This includes mutexes,
+ *              spin locks, and reader/writer locks.
  *
  ******************************************************************************/
 
@@ -107,9 +111,8 @@ void acpi_ut_mutex_terminate(void)
 
 	ACPI_FUNCTION_TRACE(ut_mutex_terminate);
 
-	/*
-	 * Delete each predefined mutex object
-	 */
+	/* Delete each predefined mutex object */
+
 	for (i = 0; i < ACPI_NUM_MUTEX; i++) {
 		(void)acpi_ut_delete_mutex(i);
 	}
@@ -118,6 +121,10 @@ void acpi_ut_mutex_terminate(void)
 
 	acpi_os_delete_lock(acpi_gbl_gpe_lock);
 	acpi_os_delete_lock(acpi_gbl_hardware_lock);
+
+	/* Delete the reader/writer lock */
+
+	acpi_ut_delete_rw_lock(&acpi_gbl_namespace_rw_lock);
 	return_VOID;
 }