linux-kernel - [PATCH V1 2/6] rpmsg: glink: Deny intent request if reusable intent fits

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Date:   Thu, 30 Jul 2020 10:48:12 +0530
From:   Deepak Kumar Singh <deesin@...eaurora.org>
To:     bjorn.andersson@...aro.org, clew@...eaurora.org
Cc:     mathieu.poirier@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Deepak Kumar Singh <deesin@...eaurora.org>
Subject: [PATCH V1 2/6] rpmsg: glink: Deny intent request if reusable intent fits

From: Chris Lew <clew@...eaurora.org>

In high traffic scenarios a remote may request extra intents to send
data faster. If the work thread that handles these intent requests is
starved of cpu time, then these requests can build up. Some remote
procs may not be able to handle this burst of built up intent requests.

In order to prevent intent build up, deny intent requests that can be
fulfilled by default intents that are reusable.

Signed-off-by: Chris Lew <clew@...eaurora.org>
Signed-off-by: Deepak Kumar Singh <deesin@...eaurora.org>
---
 drivers/rpmsg/qcom_glink_native.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
index 2668c66..df3c608 100644
--- a/drivers/rpmsg/qcom_glink_native.c
+++ b/drivers/rpmsg/qcom_glink_native.c
@@ -734,9 +734,11 @@ static void qcom_glink_handle_rx_done(struct qcom_glink *glink,
 static void qcom_glink_handle_intent_req(struct qcom_glink *glink,
 					 u32 cid, size_t size)
 {
-	struct glink_core_rx_intent *intent;
+	struct glink_core_rx_intent *intent = NULL;
+	struct glink_core_rx_intent *tmp;
 	struct glink_channel *channel;
 	unsigned long flags;
+	int iid;
 
 	spin_lock_irqsave(&glink->idr_lock, flags);
 	channel = idr_find(&glink->rcids, cid);
@@ -747,6 +749,19 @@ static void qcom_glink_handle_intent_req(struct qcom_glink *glink,
 		return;
 	}
 
+	spin_lock_irqsave(&channel->intent_lock, flags);
+	idr_for_each_entry(&channel->liids, tmp, iid) {
+		if (tmp->size >= size && tmp->reuse) {
+			intent = tmp;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&channel->intent_lock, flags);
+	if (intent) {
+		qcom_glink_send_intent_req_ack(glink, channel, !!intent);
+		return;
+	}
+
 	intent = qcom_glink_alloc_intent(glink, channel, size, false);
 	if (intent)
 		qcom_glink_advertise_intent(glink, channel, intent);
-- 
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