Added support for thread cancellation on Linux

unsupported/Eigen/CXX11/ThreadPool

@@ -50,6 +50,7 @@
 
 #include "src/ThreadPool/ThreadLocal.h"
 #include "src/ThreadPool/ThreadYield.h"
+#include "src/ThreadPool/ThreadCancel.h"
 #include "src/ThreadPool/EventCount.h"
 #include "src/ThreadPool/RunQueue.h"
 #include "src/ThreadPool/ThreadPoolInterface.h"

unsupported/Eigen/CXX11/src/ThreadPool/NonBlockingThreadPool.h

@@ -97,6 +97,12 @@ class NonBlockingThreadPoolTempl : public Eigen::ThreadPoolInterface {
       env_.ExecuteTask(t);  // Push failed, execute directly.
   }
 
+  void Cancel() {
+    for (size_t i = 0; i < threads_.size(); i++) {
+      threads_[i]->Cancel();
+    }
+  }
+
   int NumThreads() const final {
     return static_cast<int>(threads_.size());
   }

unsupported/Eigen/CXX11/src/ThreadPool/SimpleThreadPool.h

@@ -69,6 +69,12 @@ class SimpleThreadPoolTempl : public ThreadPoolInterface {
     }
   }
 
+  void Cancel() {
+    for (size_t i = 0; i < threads_.size(); i++) {
+      threads_[i]->Cancel();
+    }
+  }
+
   int NumThreads() const final {
     return static_cast<int>(threads_.size());
   }

unsupported/Eigen/CXX11/src/ThreadPool/ThreadCancel.h

@@ -0,0 +1,23 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2016 Benoit Steiner <benoit.steiner.goog@gmail.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_CXX11_THREADPOOL_THREAD_CANCEL_H
+#define EIGEN_CXX11_THREADPOOL_THREAD_CANCEL_H
+
+// Try to come up with a portable way to cancel a thread
+#if EIGEN_OS_GNULINUX
+  #define EIGEN_THREAD_CANCEL(t)                  \
+    pthread_cancel(t.native_handle());
+  #define EIGEN_SUPPORTS_THREAD_CANCELLATION 1
+#else
+#define EIGEN_THREAD_CANCEL(t)
+#endif
+
+
+#endif  // EIGEN_CXX11_THREADPOOL_THREAD_CANCEL_H

unsupported/Eigen/CXX11/src/ThreadPool/ThreadEnvironment.h

@@ -23,6 +23,7 @@ struct StlThreadEnvironment {
    public:
     EnvThread(std::function<void()> f) : thr_(std::move(f)) {}
     ~EnvThread() { thr_.join(); }
+    void Cancel() { EIGEN_THREAD_CANCEL(thr_); }
 
    private:
     std::thread thr_;

unsupported/test/cxx11_non_blocking_thread_pool.cpp

@@ -10,6 +10,7 @@
 
 #define EIGEN_USE_THREADS
 #include "main.h"
+#include <unistd.h>
 #include "Eigen/CXX11/ThreadPool"
 
 static void test_create_destroy_empty_pool()
@@ -100,8 +101,28 @@ static void test_parallelism()
   }
 }
 
+
+static void test_cancel()
+{
+  NonBlockingThreadPool tp(4);
+
+#ifdef EIGEN_SUPPORTS_THREAD_CANCELLATION
+  // Put 2 threads to sleep for much longer than the default test timeout.
+  tp.Schedule([]() { sleep(3600); } );
+  tp.Schedule([]() { sleep(3600 * 24); } );
+#else
+  // Make 2 threads sleep for a short period of time
+  tp.Schedule([]() { sleep(1); } );
+  tp.Schedule([]() { sleep(2); } );
+#endif
+
+  // Call cancel:
+  tp.Cancel();
+}
+
 void test_cxx11_non_blocking_thread_pool()
 {
   CALL_SUBTEST(test_create_destroy_empty_pool());
   CALL_SUBTEST(test_parallelism());
+  CALL_SUBTEST(test_cancel());
 }