jump_labels: API for flushing deferred jump label updates

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.

Signed-off-by: David Matlack <dmatlack@google.com>
Cc: stable@vger.kernel.org
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/jump_label_ratelimit.h b/include/linux/jump_label_ratelimit.h
index 089f70f83e97..23da3af459fe 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);
 
@@ -26,6 +27,10 @@ static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
         STATIC_KEY_CHECK_USE();
         static_key_slow_dec(&key->key);
 }
+static inline void static_key_deferred_flush(struct static_key_deferred *key)
+{
+        STATIC_KEY_CHECK_USE();
+}
 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 93ad6c1fb9b6..a9b8cf500591 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -182,6 +182,13 @@ 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)
+{
+        STATIC_KEY_CHECK_USE();
+        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)
 {