Re: [PATCH 13/18] rpmsg: glink: Add rx done command

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On 8/22/2017 7:46 PM, Sricharan R wrote:
Hi,
+    /* Take it off the tree of receive intents */
+    if (!intent->reuse) {
+        spin_lock(&channel->intent_lock);
+        idr_remove(&channel->liids, intent->id);
+        spin_unlock(&channel->intent_lock);
+    }
+
+    /* Schedule the sending of a rx_done indication */
+    spin_lock(&channel->intent_lock);
+    list_add_tail(&intent->node, &channel->done_intents);
+    spin_unlock(&channel->intent_lock);
+
+    schedule_work(&channel->intent_work);
Adding one more parallel path will hit performance, if this worker could not get CPU cycles
or blocked by other RT or HIGH_PRIO worker on global worker pool.
  The idea is, by design to have parallel non-blocking paths for rx and tx (that is done as a
  part of rx by sending the rx_done command), otherwise trying to send the rx_done
  command in the rx isr context is a problem since the tx can wait for the FIFO space and
  in worst case, can even lead to a potential deadlock if both the local and remote try
  the same. Having said that, instead of queuing this work in to the global queue, this
  can be put in to a local glink edge owned queue (or) a threaded isr ?, downstream does the
  rx_done in a client specific worker.

Yes, mixing RX and TX path will cause dead lock. I am okay to use specific queue with HIGH_PRIO or a threaded isr. down stream uses both client specific worker and client RX cb [this mix the TX and RX path] which want to avoid.

Regards,
  Sricharan


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