Re: [PATCH 04/17] powerpc/qspinlock: convert atomic operations to assembly

On Thu Nov 10, 2022 at 6:36 PM AEST, Christophe Leroy wrote:

Le 10/11/2022 à 01:39, Jordan Niethe a écrit :

quoted

quoted

+static __always_inline int trylock_clear_tail_cpu(struct qspinlock *lock, u32 old)
  {
-	int newval = _Q_LOCKED_VAL;
-
-	if (atomic_cmpxchg_acquire(&lock->val, val, newval) == val)
+	u32 new = _Q_LOCKED_VAL;
+	u32 prev;
+
+	BUG_ON(old & _Q_LOCKED_VAL);

The BUG_ON() could have been introduced in an earlier patch I think.

Can we avoid the BUG_ON() at all and replace by a WARN_ON ?

Lock has gone wrong here. Critical sections not working means data
corruption and little prospect of continuing to run.

Thanks,
Nick