On 21/09/2021 12:43, Fernand Sieber wrote:
do {
I didn't follow the full logic of this change yet ...
llq->val = READ_ONCE(cmdq->q.llq.val);
- if (!queue_full(llq))
+ if (!queue_has_space(llq, n))
But is the polarity really correct? That is, if we don't have space,
then exit with success (the function to check for space).
break;
+ /*
+ * We must return here even if there's no space, because the
producer
+ * having moved forward could mean that the last thread
observing the
+ * SMMU progress has allocated space in the cmdq and moved on,
leaving
+ * us in this waiting loop with no other thread updating
+ * llq->state->val.
what is llq->state->val?
+ */
+ if (llq->prod != prod)
+ return -EAGAIN;
+
ret = queue_poll(&qp);
Thanks,
John
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