fix race condition in cooperate

src/util/cooperate.cpp

@@ -17,24 +17,17 @@ Notes:
 
 --*/
 
+#ifndef SINGLE_THREAD
+
 #include "util/cooperate.h"
 #include "util/trace.h"
 #include "util/debug.h"
-#include <thread>
+#include <atomic>
 #include <mutex>
+#include <thread>
 
-struct cooperation_lock {
-    std::recursive_mutex m_lock;
-    char const *     m_task;
-    std::thread::id   m_owner_thread;
-    cooperation_lock() {
-        m_task = nullptr;
-    }
-    ~cooperation_lock() {
-    }
-};
-
-static cooperation_lock g_lock;
+static std::mutex lock;
+static std::atomic<std::thread::id> owner_thread;
 
 bool cooperation_ctx::g_cooperate = false;
 
@@ -42,17 +35,17 @@ void cooperation_ctx::checkpoint(char const * task) {
     SASSERT(cooperation_ctx::enabled());
 
     std::thread::id tid = std::this_thread::get_id();
-    if (g_lock.m_owner_thread == tid) {
-        g_lock.m_owner_thread = std::thread::id();
-        g_lock.m_lock.unlock();
+    if (owner_thread == tid) {
+        owner_thread = std::thread::id();
+        lock.unlock();
     }
 
     // this critical section is used to force the owner thread to give a chance to
     // another thread to get the lock
     std::this_thread::yield();
-    g_lock.m_lock.lock();
+    lock.lock();
     TRACE("cooperate_detail", tout << task << ", tid: " << tid << "\n";);
-    CTRACE("cooperate", g_lock.m_task != task, tout << "moving to task: " << task << "\n";);
-    g_lock.m_owner_thread = tid;    
+    owner_thread = tid;
 }
 
+#endif

src/util/cooperate.h

@@ -16,10 +16,9 @@ Author:
 Notes:
 
 --*/
-#ifndef COOPERATE_H_
-#define COOPERATE_H_
+#pragma once
 
-#ifndef _NO_OMP_
+#ifndef SINGLE_THREAD
 
 class cooperation_ctx {
     static bool g_cooperate;
@@ -35,5 +34,3 @@ inline void cooperate(char const * task) {
 #else
 inline void cooperate(char const *) {}
 #endif
-
-#endif