From 9f8a3553ba7e6c3ce5c9e378d77d3e16d7ce6daf Mon Sep 17 00:00:00 2001
From: Alexey Rybalchenko <alexryba@gmail.com>
Date: Thu, 16 Jan 2020 12:52:12 +0100
Subject: [PATCH] Avoid deadlock in FairMQChannel operator=, handle
 self-assignment

---
 fairmq/FairMQChannel.cxx | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fairmq/FairMQChannel.cxx b/fairmq/FairMQChannel.cxx
index 82f3b2ec..38d7c133 100644
--- a/fairmq/FairMQChannel.cxx
+++ b/fairmq/FairMQChannel.cxx
@@ -133,9 +133,15 @@ FairMQChannel::FairMQChannel(const FairMQChannel& chan, const string& newName)
 
 FairMQChannel& FairMQChannel::operator=(const FairMQChannel& chan)
 {
+    if (this == &chan) {
+        return *this;
+    }
+
     {
-        lock_guard<mutex> lock1(fMtx);
-        lock_guard<mutex> lock2(chan.fMtx);
+        // TODO: replace this with std::scoped_lock (c++17)
+        lock(fMtx, chan.fMtx);
+        lock_guard<mutex> lock1(fMtx, adopt_lock);
+        lock_guard<mutex> lock2(chan.fMtx, adopt_lock);
 
         fTransportFactory = nullptr;
         fTransportType = chan.fTransportType;