Messages in this thread | | | Subject | Re: [PATCH] iommu/arm-smmu-v3: poll cmdq until it has space | From | John Garry <> | Date | Tue, 21 Sep 2021 17:22:48 +0100 |
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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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