The second part of
if (v <= 0 || (v + 1) < 0)
is not immediately obvious that it acts as overflow protection.
Check explicitely for v == INT_MAX instead and add a proper comment how
this is used at the call sites.
Signed-off-by: Thomas Gleixner <[email protected]>
---
kernel/jump_label.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -132,12 +132,15 @@ bool static_key_fast_inc_not_disabled(st
/*
* Negative key->enabled has a special meaning: it sends
* static_key_slow_inc/dec() down the slow path, and it is non-zero
- * so it counts as "enabled" in jump_label_update(). Note that
- * atomic_inc_unless_negative() checks >= 0, so roll our own.
+ * so it counts as "enabled" in jump_label_update().
+ *
+ * The INT_MAX overflow condition is either used by the networking
+ * code to reset or detected in the slow path of
+ * static_key_slow_inc_cpuslocked().
*/
v = atomic_read(&key->enabled);
do {
- if (v <= 0 || (v + 1) < 0)
+ if (v <= 0 || v == INT_MAX)
return false;
} while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));