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>
diff --git a/drivers/acpi/acpica/nsxfeval.c b/drivers/acpi/acpica/nsxfeval.c
index 2583a66..0450540 100644
--- a/drivers/acpi/acpica/nsxfeval.c
+++ b/drivers/acpi/acpica/nsxfeval.c
@@ -475,21 +475,40 @@
}
/*
- * Lock the namespace around the walk.
- * The namespace will be unlocked/locked around each call
- * to the user function - since this function
- * must be allowed to make Acpi calls itself.
+ * Need to acquire the namespace reader lock to prevent interference
+ * with any concurrent table unloads (which causes the deletion of
+ * namespace objects). We cannot allow the deletion of a namespace node
+ * while the user function is using it. The exception to this are the
+ * nodes created and deleted during control method execution -- these
+ * nodes are marked as temporary nodes and are ignored by the namespace
+ * walk. Thus, control methods can be executed while holding the
+ * namespace deletion lock (and the user function can execute control
+ * methods.)
+ */
+ status = acpi_ut_acquire_read_lock(&acpi_gbl_namespace_rw_lock);
+ if (ACPI_FAILURE(status)) {
+ return status;
+ }
+
+ /*
+ * Lock the namespace around the walk. The namespace will be
+ * unlocked/locked around each call to the user function - since the user
+ * function must be allowed to make ACPICA calls itself (for example, it
+ * will typically execute control methods during device enumeration.)
*/
status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
if (ACPI_FAILURE(status)) {
- return_ACPI_STATUS(status);
+ goto unlock_and_exit;
}
status = acpi_ns_walk_namespace(type, start_object, max_depth,
- ACPI_NS_WALK_UNLOCK,
- user_function, context, return_value);
+ ACPI_NS_WALK_UNLOCK, user_function,
+ context, return_value);
(void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
+
+ unlock_and_exit:
+ (void)acpi_ut_release_read_lock(&acpi_gbl_namespace_rw_lock);
return_ACPI_STATUS(status);
}