[PATCH 3.12 151/235] jump_labels: API for flushing deferred jump label updates

[Jiri Slaby]

From: David Matlack <dmatlack@xxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit b6416e61012429e0277bd15a229222fd17afc1c1 upstream.

Modules that use static_key_deferred need a way to synchronize with
any delayed work that is still pending when the module is unloaded.
Introduce static_key_deferred_flush() which flushes any pending
jump label updates.

[js] no STATIC_KEY_CHECK_USE in 3.12 -> remove it

Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 include/linux/jump_label_ratelimit.h | 4 ++++
 kernel/jump_label.c                  | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/jump_label_ratelimit.h b/include/linux/jump_label_ratelimit.h
index 113788389b3d..3f66ce8f0819 100644
--- a/include/linux/jump_label_ratelimit.h
+++ b/include/linux/jump_label_ratelimit.h
@@ -14,6 +14,7 @@ struct static_key_deferred {
 
 #ifdef HAVE_JUMP_LABEL
 extern void static_key_slow_dec_deferred(struct static_key_deferred *key);
+extern void static_key_deferred_flush(struct static_key_deferred *key);
 extern void
 jump_label_rate_limit(struct static_key_deferred *key, unsigned long rl);
 
@@ -25,6 +26,9 @@ static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
 {
 	static_key_slow_dec(&key->key);
 }
+static inline void static_key_deferred_flush(struct static_key_deferred *key)
+{
+}
 static inline void
 jump_label_rate_limit(struct static_key_deferred *key,
 		unsigned long rl)
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 297a9247a3b3..9ce813e99a56 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -113,6 +113,12 @@ void static_key_slow_dec_deferred(struct static_key_deferred *key)
 }
 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
 
+void static_key_deferred_flush(struct static_key_deferred *key)
+{
+	flush_delayed_work(&key->work);
+}
+EXPORT_SYMBOL_GPL(static_key_deferred_flush);
+
 void jump_label_rate_limit(struct static_key_deferred *key,
 		unsigned long rl)
 {
-- 
2.11.0