path: root/kernel/jump_label.c
diff options
authorHannes Frederic Sowa <>2013-10-19 21:48:53 +0200
committerDavid S. Miller <>2013-10-19 19:45:35 -0400
commitc4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d (patch)
tree37d56a25f147e626b68532543c8569a739f7fee3 /kernel/jump_label.c
parentb50026b5ac8fe2932e6af0c54b21da0913c4c1c7 (diff)
static_key: WARN on usage before jump_label_init was called
Usage of the static key primitives to toggle a branch must not be used before jump_label_init() is called from init/main.c. jump_label_init reorganizes and wires up the jump_entries so usage before that could have unforeseen consequences. Following primitives are now checked for correct use: * static_key_slow_inc * static_key_slow_dec * static_key_slow_dec_deferred * jump_label_rate_limit The x86 architecture already checks this by testing if the default_nop was already replaced with an optimal nop or with a branch instruction. It will panic then. Other architectures don't check for this. Because we need to relax this check for the x86 arch to allow code to transition from default_nop to the enabled state and other architectures did not check for this at all this patch introduces checking on the static_key primitives in a non-arch dependent manner. All checked functions are considered slow-path so the additional check does no harm to performance. The warnings are best observed with earlyprintk. Based on a patch from Andi Kleen. Cc: Steven Rostedt <> Cc: Peter Zijlstra <> Cc: Andi Kleen <> Signed-off-by: Hannes Frederic Sowa <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'kernel/jump_label.c')
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 297a9247a3b3..9019f15deab2 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -58,6 +58,7 @@ static void jump_label_update(struct static_key *key, int enable);
void static_key_slow_inc(struct static_key *key)
if (atomic_inc_not_zero(&key->enabled))
@@ -103,12 +104,14 @@ static void jump_label_update_timeout(struct work_struct *work)
void static_key_slow_dec(struct static_key *key)
__static_key_slow_dec(key, 0, NULL);
void static_key_slow_dec_deferred(struct static_key_deferred *key)
__static_key_slow_dec(&key->key, key->timeout, &key->work);
@@ -116,6 +119,7 @@ EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
void jump_label_rate_limit(struct static_key_deferred *key,
unsigned long rl)
key->timeout = rl;
INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
@@ -212,6 +216,7 @@ void __init jump_label_init(void)
key->next = NULL;
+ static_key_initialized = true;