On 3/6/23 14:33, Paolo Bonzini wrote:
@@ -107,11 +114,8 @@ static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags) QSLIST_REMOVE_HEAD(head, next);/*- * The qatomic_and is paired with aio_bh_enqueue(). The implicit memory - * barrier ensures that the callback sees all writes done by the scheduling - * thread. It also ensures that the scheduling thread sees the cleared - * flag before bh->cb has run, and thus will call aio_notify again if - * necessary. + * Synchronizes with qatomic_fetch_or() in aio_bh_enqueue(), ensuring that + * the removal finishes before BH_PENDING is reset. */ *flags = qatomic_fetch_and(&bh->flags,
Per this new comment, about the remove finishing first, it would seem that we need smp_mb__before_rmw here, because QSLIST_REMOVE_HEAD is not SEQCST.
r~
