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, 37 insertions, 8 deletions

diff --git a/drivers/acpi/acpica/tbinstal.c b/drivers/acpi/acpica/tbinstal.c
index c37993003f2c..f865d5a096de 100644
--- a/drivers/acpi/acpica/tbinstal.c
+++ b/drivers/acpi/acpica/tbinstal.c
@@ -434,27 +434,56 @@ void acpi_tb_terminate(void)
  *
  * PARAMETERS:  table_index         - Table index
  *
- * RETURN:      None
+ * RETURN:      Status
  *
  * DESCRIPTION: Delete all namespace objects created when this table was loaded.
  *
  ******************************************************************************/
 
-void acpi_tb_delete_namespace_by_owner(u32 table_index)
+acpi_status acpi_tb_delete_namespace_by_owner(u32 table_index)
 {
         acpi_owner_id owner_id;
+        acpi_status status;
+
+        ACPI_FUNCTION_TRACE(tb_delete_namespace_by_owner);
+
+        status = acpi_ut_acquire_mutex(ACPI_MTX_TABLES);
+        if (ACPI_FAILURE(status)) {
+                return_ACPI_STATUS(status);
+        }
+
+        if (table_index >= acpi_gbl_root_table_list.count) {
+
+                /* The table index does not exist */
 
-        (void)acpi_ut_acquire_mutex(ACPI_MTX_TABLES);
-        if (table_index < acpi_gbl_root_table_list.count) {
-                owner_id =
-                    acpi_gbl_root_table_list.tables[table_index].owner_id;
-        } else {
                 (void)acpi_ut_release_mutex(ACPI_MTX_TABLES);
-                return;
+                return_ACPI_STATUS(AE_NOT_EXIST);
         }
 
+        /* Get the owner ID for this table, used to delete namespace nodes */
+
+        owner_id = acpi_gbl_root_table_list.tables[table_index].owner_id;
         (void)acpi_ut_release_mutex(ACPI_MTX_TABLES);
+
+        /*
+         * Need to acquire the namespace writer lock to prevent interference
+         * with any concurrent namespace walks. The interpreter must be
+         * released during the deletion since the acquisition of the deletion
+         * lock may block, and also since the execution of a namespace walk
+         * must be allowed to use the interpreter.
+         */
+        acpi_ut_release_mutex(ACPI_MTX_INTERPRETER);
+        status = acpi_ut_acquire_write_lock(&acpi_gbl_namespace_rw_lock);
+
         acpi_ns_delete_namespace_by_owner(owner_id);
+        if (ACPI_FAILURE(status)) {
+                return_ACPI_STATUS(status);
+        }
+
+        acpi_ut_release_write_lock(&acpi_gbl_namespace_rw_lock);
+
+        status = acpi_ut_acquire_mutex(ACPI_MTX_INTERPRETER);
+        return_ACPI_STATUS(status);
 }
 
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