The sequence
static DEFINE_WW_CLASS(test_ww_class);
struct ww_acquire_ctx ww_ctx;
struct ww_mutex ww_lock_a;
struct ww_mutex ww_lock_b;
struct ww_mutex ww_lock_c;
struct mutex lock_c;
ww_acquire_init(&ww_ctx, &test_ww_class);
ww_mutex_init(&ww_lock_a, &test_ww_class);
ww_mutex_init(&ww_lock_b, &test_ww_class);
ww_mutex_init(&ww_lock_c, &test_ww_class);
mutex_init(&lock_c);
WARN_ON(ww_mutex_lock(&ww_lock_a, &ww_ctx));
WARN_ON(!mutex_trylock(&lock_c));
WARN_ON(ww_mutex_lock(&ww_lock_b, &ww_ctx));
WARN_ON(ww_mutex_lock(&ww_lock_c, &ww_ctx));
mutex_unlock(&lock_c); (*)
ww_mutex_unlock(&ww_lock_c);
ww_mutex_unlock(&ww_lock_b);
ww_mutex_unlock(&ww_lock_a);
ww_acquire_fini(&ww_ctx); (**)
will trigger the following error in __lock_release() when calling
mutex_release() at **:
DEBUG_LOCKS_WARN_ON(depth <= 0)
The problem is that the hlock merging happening at * updates the
references for test_ww_class incorrectly to 3 whereas it should've
updated it to 4 (representing all the instances for ww_ctx and
ww_lock_[abc]).
Fix this by updating the references during merging correctly taking into
account that we can have non-zero references (both for the hlock that we
merge into another hlock or for the hlock we are mering into).
Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Imre Deak <imre.d...@intel.com>
---
kernel/locking/lockdep.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 967352d32af1..9e2a4ab6c731 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3637,6 +3637,11 @@ print_lock_nested_lock_not_held(struct task_struct *curr,
static int __lock_is_held(const struct lockdep_map *lock, int read);
+static int hlock_reference(int reference)
+{
+ return reference ? : 1;
+}
+
/*
* This gets called for every mutex_lock*()/spin_lock*() operation.
* We maintain the dependency maps and validate the locking attempt:
@@ -3702,17 +3707,15 @@ static int __lock_acquire(struct lockdep_map *lock,
unsigned int subclass,
if (depth) {
hlock = curr->held_locks + depth - 1;
if (hlock->class_idx == class_idx && nest_lock) {
- if (hlock->references) {
- /*
- * Check: unsigned int references overflow.
- */
- if (DEBUG_LOCKS_WARN_ON(hlock->references ==
UINT_MAX))
- return 0;
+ /*
+ * Check: unsigned int references overflow.
+ */
+ if
(DEBUG_LOCKS_WARN_ON(hlock_reference(hlock->references) >
+ UINT_MAX -
hlock_reference(references)))
+ return 0;
- hlock->references++;
- } else {
- hlock->references = 2;
- }
+ hlock->references = hlock_reference(hlock->references) +
+ hlock_reference(references);
return 2;
}
--
2.17.1
