ACPICA: Allow same ACPI table to be loaded/unloaded more than once

Without this change, a table cannot be loaded again once it has
been loaded/unloaded one time. The current mechanism does not
unregister a table upon an unload. During a load, if the same
table is found, this no longer returns an exception.

http://www.acpica.org/bugzilla/show_bug.cgi?id=722

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

1 files changed, 42 insertions, 7 deletions

diff --git a/drivers/acpi/tables/tbinstal.c b/drivers/acpi/tables/tbinstal.c
index b22185f55a1..905dc38ab23 100644
--- a/drivers/acpi/tables/tbinstal.c
+++ b/drivers/acpi/tables/tbinstal.c
@@ -145,6 +145,8 @@ acpi_tb_add_table(struct acpi_table_desc *table_desc, u32 *table_index)
                         }
                 }
 
+                /* Check for a table match on the entire table length */
+
                 length = ACPI_MIN(table_desc->length,
                                   acpi_gbl_root_table_list.tables[i].length);
                 if (ACPI_MEMCMP(table_desc->pointer,
@@ -153,17 +155,49 @@ acpi_tb_add_table(struct acpi_table_desc *table_desc, u32 *table_index)
                         continue;
                 }
 
-                /* Table is already registered */
-
+                /*
+                 * Note: the current mechanism does not unregister a table if it is
+                 * dynamically unloaded. The related namespace entries are deleted,
+                 * but the table remains in the root table list.
+                 *
+                 * The assumption here is that the number of different tables that
+                 * will be loaded is actually small, and there is minimal overhead
+                 * in just keeping the table in case it is needed again.
+                 *
+                 * If this assumption changes in the future (perhaps on large
+                 * machines with many table load/unload operations), tables will
+                 * need to be unregistered when they are unloaded, and slots in the
+                 * root table list should be reused when empty.
+                 */
+
+                /*
+                 * Table is already registered.
+                 * We can delete the table that was passed as a parameter.
+                 */
                 acpi_tb_delete_table(table_desc);
                 *table_index = i;
-                status = AE_ALREADY_EXISTS;
-                goto release;
+
+                if (acpi_gbl_root_table_list.tables[i].
+                    flags & ACPI_TABLE_IS_LOADED) {
+
+                        /* Table is still loaded, this is an error */
+
+                        status = AE_ALREADY_EXISTS;
+                        goto release;
+                } else {
+                        /* Table was unloaded, allow it to be reloaded */
+
+                        table_desc->pointer =
+                            acpi_gbl_root_table_list.tables[i].pointer;
+                        table_desc->address =
+                            acpi_gbl_root_table_list.tables[i].address;
+                        status = AE_OK;
+                        goto print_header;
+                }
         }
 
-        /*
-         * Add the table to the global table list
-         */
+        /* Add the table to the global root table list */
+
         status = acpi_tb_store_table(table_desc->address, table_desc->pointer,
                                      table_desc->length, table_desc->flags,
                                      table_index);
@@ -171,6 +205,7 @@ acpi_tb_add_table(struct acpi_table_desc *table_desc, u32 *table_index)
                 goto release;
         }
 
+      print_header:
         acpi_tb_print_table_header(table_desc->address, table_desc->pointer);
 
       release: