From 31e6acb949293d53ca61a6358ad886433092fe3c Mon Sep 17 00:00:00 2001
From: Rebecca Pelke <rebecca.pelke@rwth-aachen.de>
Date: Mon, 27 Jul 2020 18:14:51 +0200
Subject: [PATCH] umd: sync taskQueue operations in Emulator using condition
 variables

---
 umd/core/src/runtime/Emulator.cpp            | 44 +++++++++++---------
 umd/core/src/runtime/include/priv/Emulator.h |  5 +++
 2 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/umd/core/src/runtime/Emulator.cpp b/umd/core/src/runtime/Emulator.cpp
index 6121c13d..e94f2b0a 100644
--- a/umd/core/src/runtime/Emulator.cpp
+++ b/umd/core/src/runtime/Emulator.cpp
@@ -60,13 +60,16 @@ bool Emulator::ping()
 
 NvDlaError Emulator::submit(NvU8* task_mem, bool blocking)
 {
-    m_taskQueue.push(task_mem);
+    {
+        std::lock_guard<std::mutex> lk(m_mtx); 
+        m_taskQueue.push(task_mem);
+    }
 
+    m_cv.notify_all(); 
     if (blocking) {
-        // wait until queue becomes empty
-        while (!m_taskQueue.empty()) {
-            NvDlaThreadYield();
-        }
+        // wait until queue becomes empty  
+        std::unique_lock<std::mutex> lk(m_mtx);
+        m_cv.wait(lk, [&]{return !(!m_taskQueue.empty() || m_signalShutdown);});       
     }
 
     return NvDlaSuccess;
@@ -97,6 +100,7 @@ bool Emulator::stop()
     if (m_thread)
     {
         m_signalShutdown = true;
+        m_cv.notify_all();          
         NvDlaThreadJoin(m_thread);
         m_thread = NULL;
     }
@@ -115,7 +119,14 @@ bool Emulator::run()
 
     while (true)
     {
-        if (!m_taskQueue.empty())
+        std::unique_lock<std::mutex> lk(m_mtx);
+        m_cv.wait(lk, [&]{return (!m_taskQueue.empty() || m_signalShutdown);});
+
+        if (m_signalShutdown) 
+        {
+            break; 
+        }
+        else if (!m_taskQueue.empty())
         {
             NvU8* task_mem = m_taskQueue.front();
             NvDlaDebugPrintf("Work Found!\n");
@@ -145,25 +156,18 @@ bool Emulator::run()
             NvDlaDebugPrintf("Work Done\n");
 
             m_taskQueue.pop();
-            continue;
-        }
-
-        if (m_signalShutdown)
-        {
-            NvDlaDebugPrintf("Shutdown signal received, exiting\n");
-            break;
+            m_cv.notify_one();
         }
+    } 
 
-        if (m_taskQueue.empty())
-        {
-            NvDlaSleepMS(500);
-        }
-    }
 
     // Cleanup
-    while (!m_taskQueue.empty())
     {
-        m_taskQueue.pop();
+        std::lock_guard<std::mutex> lk(m_mtx);
+        while (!m_taskQueue.empty())
+        {
+            m_taskQueue.pop();
+        }
     }
 
     delete emu_if;
diff --git a/umd/core/src/runtime/include/priv/Emulator.h b/umd/core/src/runtime/include/priv/Emulator.h
index c21d9f13..8e137c85 100644
--- a/umd/core/src/runtime/include/priv/Emulator.h
+++ b/umd/core/src/runtime/include/priv/Emulator.h
@@ -30,6 +30,8 @@
 #define NVDLA_PRIV_EMULATOR_H
 
 #include <queue>
+#include <mutex>
+#include <condition_variable>
 
 #include "priv/EMUInterface.h"
 
@@ -78,6 +80,9 @@ class Emulator
     bool m_threadActive;
 
     bool m_signalShutdown;
+
+    std::mutex m_mtx;
+    std::condition_variable m_cv;
 };
 
 } // nvdla::priv