rethook: Reject getting a rethook if RCU is not watching

[linux-2.6-microblaze.git] / kernel / trace / rethook.c

diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
index b568337..c69d822 100644 (file)
--- a/kernel/trace/rethook.c
+++ b/kernel/trace/rethook.c
@@ -154,6 +154,15 @@ struct rethook_node *rethook_try_get(struct rethook *rh)
        if (unlikely(!handler))
                return NULL;
 
+       /*
+        * This expects the caller will set up a rethook on a function entry.
+        * When the function returns, the rethook will eventually be reclaimed
+        * or released in the rethook_recycle() with call_rcu().
+        * This means the caller must be run in the RCU-availabe context.
+        */
+       if (unlikely(!rcu_is_watching()))
+               return NULL;
+
        fn = freelist_try_get(&rh->pool);
        if (!fn)
                return NULL;