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Subject[PATCH] jump_labels: Add WARN_ON for too early jump label use
I spent a few hours tracking down a regression in my TSX code,
which turned out that it is not legal anymore to change jump
labels before the jump label code is initialized.

Add a WARN_ON() for this case.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 297a924..c6c5290 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -17,6 +17,8 @@

#ifdef HAVE_JUMP_LABEL

+static bool jump_label_initialized;
+
/* mutex to protect coming/going of the the jump_label table */
static DEFINE_MUTEX(jump_label_mutex);

@@ -58,6 +60,8 @@ static void jump_label_update(struct static_key *key, int enable);

void static_key_slow_inc(struct static_key *key)
{
+ WARN_ON(!jump_label_initialized);
+
if (atomic_inc_not_zero(&key->enabled))
return;

@@ -76,6 +80,7 @@ EXPORT_SYMBOL_GPL(static_key_slow_inc);
static void __static_key_slow_dec(struct static_key *key,
unsigned long rate_limit, struct delayed_work *work)
{
+ WARN_ON(!jump_label_initialized);
if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
WARN(atomic_read(&key->enabled) < 0,
"jump label: negative count!\n");
@@ -213,6 +218,7 @@ void __init jump_label_init(void)
#endif
}
jump_label_unlock();
+ jump_label_initialized = true;
}

#ifdef CONFIG_MODULES
--
ak@linux.intel.com -- Speaking for myself only

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