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

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Date:   Tue, 22 Aug 2017 19:46:00 +0530
From:   Sricharan R <sricharan@...eaurora.org>
To:     Arun Kumar Neelakantam <aneela@...eaurora.org>, ohad@...ery.com,
        bjorn.andersson@...aro.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 13/18] rpmsg: glink: Add rx done command

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.

Regards,
 Sricharan

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