Merge pull request #342 from ChrisCatCP/master

refactor wait_group

lib_fiber/cpp/include/fiber/wait_group.hpp

@@ -1,4 +1,5 @@
 #pragma once
+#include "acl_cpp/stdlib/atomic.hpp"
 
 namespace acl {
 
@@ -9,12 +10,12 @@ class wait_group {
 	wait_group(void);
 	~wait_group(void);
 
-	void add(size_t n);
+	void add(int n);
 	void done(void);
-	size_t wait(void);
+	void wait(void);
 
 private:
-	size_t count_;
+	atomic_long state_;
 	fiber_tbox<unsigned long>* box_;
 };
 

lib_fiber/cpp/src/wait_group.cpp

@@ -6,7 +6,7 @@ namespace acl {
 
 wait_group::wait_group(void)
 {
-	count_ = 0;
+	state_ = 0;
 	box_   = new acl::fiber_tbox<unsigned long>;
 }
 
@@ -15,37 +15,70 @@ wait_group::~wait_group(void)
 	delete box_;
 }
 
-void wait_group::add(size_t n)
+void wait_group::add(int n)
 {
-	count_ += n;
+    long long state = state_.add_fetch((long long)n << 32);
+	//高32位为任务数量
+    int c = (int)(state >> 32);
+	//低32位为等待者数量
+    uint32_t w =  (uint32_t)state;
+	//count不能小于0
+    if(c < 0){
+        acl_msg_fatal("wait_group: negative wait_group counter");
+    }
+    if(w != 0 && n > 0 && c == n){
+        acl_msg_fatal("wait_group: add called concurrently with wait");
+    }
+    if(c > 0 || w ==0){
+        return;
+    }
+	//检查state是否被修改
+    if(state_ != state){
+        acl_msg_fatal("wait_group: add called concurrently with wait");
+    }
+	//这里count为0了，清空state并唤醒所有等待者
+    state_ = 0;
+    for (size_t i = 0; i < w; i++) {
+#ifdef	_DEBUG
+        unsigned long* tid = new unsigned long;
+        *tid = acl::thread::self();
+        box_->push(tid);
+#else
+        box_->push(NULL);
+#endif
+    }
 }
 
 void wait_group::done(void)
 {
-#ifdef	_DEBUG
-	unsigned long* tid = new unsigned long;
-	*tid = acl::thread::self();
-	box_->push(tid);
-#else
-	box_->push(NULL);
-#endif
+    add(-1);
 }
 
-size_t wait_group::wait(void)
+void wait_group::wait(void)
 {
-	size_t i;
-	for (i = 0; i < count_; i++) {
-		bool found;
+    for(;;){
+        long long state = state_;
+        int c = (int)(state >> 32);
+        uint32_t w =  (uint32_t)state;
+		//没有任务直接返回
+        if(c == 0) return;
+		//等待者数量加一，失败的话重新获取state
+        if(state_.cas(state, state + 1) == state){
+            bool found;
 #ifdef	_DEBUG
-		unsigned long* tid = box_->pop(-1, &found);
-		assert(found);
-		delete tid;
+            unsigned long* tid = box_->pop(-1, &found);
+            assert(found);
+            delete tid;
 #else
-		(void) box_->pop(-1, &found);
-		assert(found);
+            (void) box_->pop(-1, &found);
+            assert(found);
 #endif
-	}
-	return i;
+            if(state_ != 0){
+                acl_msg_fatal("wait_group: wait_group is reused before previous wait has returned");
+            }
+            return;
+        }
+    }
 }
 
 } // namespace acl

lib_fiber/samples/wait_group/main.cpp

@@ -71,7 +71,7 @@ class fiber_waiter : public acl::fiber
 	// @override
 	void run(void) {
 		size_t ret = sync_.wait();
-		printf("All threads and fibers were done, ret=%zd\r\n", ret);
+		printf("All threads and fibers were done\r\n");
 	}
 };