abstract_tcp_server2: avoid deadlock waiting for send queue to drain

If we reach the send queue size limit, we need to release the lock,
or we will deadlock and it will never drain.

If we reach that limit, it's likely there's another problem in the
first place though, so it will probably not drain in practice either,
unless some kind of transient network timeout.

1 files changed, 5 insertions, 2 deletions

diff --git a/contrib/epee/include/net/abstract_tcp_server2.inl b/contrib/epee/include/net/abstract_tcp_server2.inl
index b3d4e5fdb..416a24739 100644
--- a/contrib/epee/include/net/abstract_tcp_server2.inl
+++ b/contrib/epee/include/net/abstract_tcp_server2.inl
@@ -490,7 +490,9 @@ PRAGMA_WARNING_DISABLE_VS(4355)
 			sleep_before_packet(cb, 1, 1);
 		}
 
-    epee::critical_region_t<decltype(m_send_que_lock)> send_guard(m_send_que_lock); // *** critical ***
+    m_send_que_lock.lock(); // *** critical ***
+    epee::misc_utils::auto_scope_leave_caller scope_exit_handler = epee::misc_utils::create_scope_leave_handler([&](){m_send_que_lock.unlock();});
+
     long int retry=0;
     const long int retry_limit = 5*4;
     while (m_send_que.size() > ABSTRACT_SERVER_SEND_QUE_MAX_COUNT)
@@ -504,11 +506,12 @@ PRAGMA_WARNING_DISABLE_VS(4355)
 
         long int ms = 250 + (rand()%50);
         _info_c("net/sleep", "Sleeping because QUEUE is FULL, in " << __FUNCTION__ << " for " << ms << " ms before packet_size="<<cb); // XXX debug sleep
+        m_send_que_lock.unlock();
         boost::this_thread::sleep(boost::posix_time::milliseconds( ms ) );
+        m_send_que_lock.lock();
         _dbg1("sleep for queue: " << ms);
 
         if (retry > retry_limit) {
-            send_guard.unlock();
             _erro("send que size is more than ABSTRACT_SERVER_SEND_QUE_MAX_COUNT(" << ABSTRACT_SERVER_SEND_QUE_MAX_COUNT << "), shutting down connection");
             //	_dbg1_c("net/sleep", "send que size is more than ABSTRACT_SERVER_SEND_QUE_MAX_COUNT(" << ABSTRACT_SERVER_SEND_QUE_MAX_COUNT << "), shutting down connection");
             close();