jump_label: add arch_jump_label_transform_static() to optimise non-live code updates
When updating a newly loaded module, the code is definitely not yet
executing on any processor, so it can be updated with no need for any
heavyweight synchronization.
This patch adds arch_jump_label_static() which is implemented as
arch_jump_label_transform() by default, but architectures can override
it if it avoids, say, a call to stop_machine().
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 059202d5..ff2028f 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -104,6 +104,18 @@
return 0;
}
+/*
+ * Update code which is definitely not currently executing.
+ * Architectures which need heavyweight synchronization to modify
+ * running code can override this to make the non-live update case
+ * cheaper.
+ */
+void __weak arch_jump_label_transform_static(struct jump_entry *entry,
+ enum jump_label_type type)
+{
+ arch_jump_label_transform(entry, type);
+}
+
static void __jump_label_update(struct jump_label_key *key,
struct jump_entry *entry,
struct jump_entry *stop, int enable)
@@ -135,8 +147,8 @@
struct jump_label_key *iterk;
iterk = (struct jump_label_key *)(unsigned long)iter->key;
- arch_jump_label_transform(iter, jump_label_enabled(iterk) ?
- JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
+ arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
+ JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
if (iterk == key)
continue;
@@ -208,7 +220,7 @@
return;
for (iter = iter_start; iter < iter_stop; iter++)
- arch_jump_label_transform(iter, JUMP_LABEL_DISABLE);
+ arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
}
static int jump_label_add_module(struct module *mod)