From e3cf7567856267bc4f4af0f1fb857cab105602e8 Mon Sep 17 00:00:00 2001
From: Adam Ierymenko <adam.ierymenko@gmail.com>
Date: Tue, 8 Aug 2017 13:21:10 -0700
Subject: Make rxQueue lock-free using an atomic counter ring buffer.

---
 node/Switch.cpp | 36 +++++++++++-------------------------
 1 file changed, 11 insertions(+), 25 deletions(-)

(limited to 'node/Switch.cpp')

diff --git a/node/Switch.cpp b/node/Switch.cpp
index 9c9daac9..c509ef16 100644
--- a/node/Switch.cpp
+++ b/node/Switch.cpp
@@ -120,10 +120,8 @@ void Switch::onRemotePacket(void *tPtr,const int64_t localSocket,const InetAddre
 						// Total fragments must be more than 1, otherwise why are we
 						// seeing a Packet::Fragment?
 
-						Mutex::Lock _l(_rxQueue_m);
-						RXQueueEntry *const rq = _findRXQueueEntry(now,fragmentPacketId);
-
-						if ((!rq->timestamp)||(rq->packetId != fragmentPacketId)) {
+						RXQueueEntry *const rq = _findRXQueueEntry(fragmentPacketId);
+						if (rq->packetId != fragmentPacketId) {
 							// No packet found, so we received a fragment without its head.
 
 							rq->timestamp = now;
@@ -250,10 +248,8 @@ void Switch::onRemotePacket(void *tPtr,const int64_t localSocket,const InetAddre
 						((uint64_t)reinterpret_cast<const uint8_t *>(data)[7])
 					);
 
-					Mutex::Lock _l(_rxQueue_m);
-					RXQueueEntry *const rq = _findRXQueueEntry(now,packetId);
-
-					if ((!rq->timestamp)||(rq->packetId != packetId)) {
+					RXQueueEntry *const rq = _findRXQueueEntry(packetId);
+					if (rq->packetId != packetId) {
 						// If we have no other fragments yet, create an entry and save the head
 
 						rq->timestamp = now;
@@ -286,14 +282,7 @@ void Switch::onRemotePacket(void *tPtr,const int64_t localSocket,const InetAddre
 					// Packet is unfragmented, so just process it
 					IncomingPacket packet(data,len,path,now);
 					if (!packet.tryDecode(RR,tPtr)) {
-						Mutex::Lock _l(_rxQueue_m);
-						RXQueueEntry *rq = &(_rxQueue[ZT_RX_QUEUE_SIZE - 1]);
-						unsigned long i = ZT_RX_QUEUE_SIZE - 1;
-						while ((i)&&(rq->timestamp)) {
-							RXQueueEntry *tmp = &(_rxQueue[--i]);
-							if (tmp->timestamp < rq->timestamp)
-								rq = tmp;
-						}
+						RXQueueEntry *const rq = _nextRXQueueEntry();
 						rq->timestamp = now;
 						rq->packetId = packet.packetId();
 						rq->frag0 = packet;
@@ -590,15 +579,12 @@ void Switch::doAnythingWaitingForPeer(void *tPtr,const SharedPtr<Peer> &peer)
 		_outstandingWhoisRequests.erase(peer->address());
 	}
 
-	{	// finish processing any packets waiting on peer's public key / identity
-		Mutex::Lock _l(_rxQueue_m);
-		unsigned long i = ZT_RX_QUEUE_SIZE;
-		while (i) {
-			RXQueueEntry *rq = &(_rxQueue[--i]);
-			if ((rq->timestamp)&&(rq->complete)) {
-				if (rq->frag0.tryDecode(RR,tPtr))
-					rq->timestamp = 0;
-			}
+	// finish processing any packets waiting on peer's public key / identity
+	for(unsigned int ptr=0;ptr<ZT_RX_QUEUE_SIZE;++ptr) {
+		RXQueueEntry *const rq = &(_rxQueue[ptr]);
+		if ((rq->timestamp)&&(rq->complete)) {
+			if (rq->frag0.tryDecode(RR,tPtr))
+				rq->timestamp = 0;
 		}
 	}
 
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