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Diffstat (limited to 'kernel/jump_label.c')
-rw-r--r--kernel/jump_label.c34
1 files changed, 27 insertions, 7 deletions
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 6dc76b590703..93a822d3c468 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -168,7 +168,7 @@ bool static_key_slow_inc_cpuslocked(struct static_key *key)
jump_label_update(key);
/*
* Ensure that when static_key_fast_inc_not_disabled() or
- * static_key_slow_try_dec() observe the positive value,
+ * static_key_dec_not_one() observe the positive value,
* they must also observe all the text changes.
*/
atomic_set_release(&key->enabled, 1);
@@ -250,7 +250,7 @@ void static_key_disable(struct static_key *key)
}
EXPORT_SYMBOL_GPL(static_key_disable);
-static bool static_key_slow_try_dec(struct static_key *key)
+static bool static_key_dec_not_one(struct static_key *key)
{
int v;
@@ -274,6 +274,14 @@ static bool static_key_slow_try_dec(struct static_key *key)
* enabled. This suggests an ordering problem on the user side.
*/
WARN_ON_ONCE(v < 0);
+
+ /*
+ * Warn about underflow, and lie about success in an attempt to
+ * not make things worse.
+ */
+ if (WARN_ON_ONCE(v == 0))
+ return true;
+
if (v <= 1)
return false;
} while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v - 1)));
@@ -284,15 +292,27 @@ static bool static_key_slow_try_dec(struct static_key *key)
static void __static_key_slow_dec_cpuslocked(struct static_key *key)
{
lockdep_assert_cpus_held();
+ int val;
- if (static_key_slow_try_dec(key))
+ if (static_key_dec_not_one(key))
return;
guard(mutex)(&jump_label_mutex);
- if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
+ val = atomic_read(&key->enabled);
+ /*
+ * It should be impossible to observe -1 with jump_label_mutex held,
+ * see static_key_slow_inc_cpuslocked().
+ */
+ if (WARN_ON_ONCE(val == -1))
+ return;
+ /*
+ * Cannot already be 0, something went sideways.
+ */
+ if (WARN_ON_ONCE(val == 0))
+ return;
+
+ if (atomic_dec_and_test(&key->enabled))
jump_label_update(key);
- else
- WARN_ON_ONCE(!static_key_slow_try_dec(key));
}
static void __static_key_slow_dec(struct static_key *key)
@@ -329,7 +349,7 @@ void __static_key_slow_dec_deferred(struct static_key *key,
{
STATIC_KEY_CHECK_USE(key);
- if (static_key_slow_try_dec(key))
+ if (static_key_dec_not_one(key))
return;
schedule_delayed_work(work, timeout);