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Fix logic bugs and destruction safety in block_queue #321

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Fix logic bugs and destruction safety in block_queue #321

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75 changes: 56 additions & 19 deletions log/block_queue.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ class block_queue
{
if (max_size <= 0)
{
std::cerr << "Fatal Error: block_queue init (max_size <= 0)" << std::endl;
exit(-1);
}

Expand All @@ -29,6 +30,7 @@ class block_queue
m_size = 0;
m_front = -1;
m_back = -1;
m_close = false;
}

void clear()
Expand All @@ -40,14 +42,17 @@ class block_queue
m_mutex.unlock();
}

~block_queue()
{
~block_queue() {
m_mutex.lock();
if (m_array != NULL)
m_close = true;
m_cond.broadcast(); // 强行叫醒所有还在睡觉的 pop 线程
if (m_array != NULL){
delete [] m_array;

m_array = NULL;
}
m_mutex.unlock();
}

//判断队列是否满了
bool full()
{
Expand Down Expand Up @@ -77,20 +82,24 @@ class block_queue
bool front(T &value)
{
m_mutex.lock();
if (0 == m_size)
// check: 如果队列已关闭或为空，直接返回
if (m_close || 0 == m_size)
{
m_mutex.unlock();
return false;
}
value = m_array[m_front];
// 求队首元素索引
int index = ( m_front +1 ) % m_max_size;
value = m_array[index];
m_mutex.unlock();
return true;
}
//返回队尾元素
bool back(T &value)
{
m_mutex.lock();
if (0 == m_size)
// check: 如果队列已关闭或为空，直接返回
if (m_close || 0 == m_size)
{
m_mutex.unlock();
return false;
Expand Down Expand Up @@ -128,6 +137,13 @@ class block_queue
{

m_mutex.lock();

// check: 如果队列已关闭，直接返回
if (m_close) {
m_mutex.unlock();
return false;
}

if (m_size >= m_max_size)
{

Expand All @@ -141,7 +157,7 @@ class block_queue

m_size++;

m_cond.broadcast();
m_cond.signal(); // 减少唤醒多个线程带来的可能额外性能损耗
m_mutex.unlock();
return true;
}
Expand All @@ -151,15 +167,26 @@ class block_queue

m_mutex.lock();
while (m_size <= 0)
{

{
// check: 直接退出返回
if (m_close) {
m_mutex.unlock();
return false;
}

if (!m_cond.wait(m_mutex.get()))
{
m_mutex.unlock();
return false;
}
}

// check：从 wait 醒来后，可能资源已被析构，必须再次判断
if (m_close) {
m_mutex.unlock();
return false;
}

m_front = (m_front + 1) % m_max_size;
item = m_array[m_front];
m_size--;
Expand All @@ -173,20 +200,29 @@ class block_queue
struct timespec t = {0, 0};
struct timeval now = {0, 0};
gettimeofday(&now, NULL);

long long total_ns = (now.tv_usec * 1000LL) + ((ms_timeout % 1000) * 1000000LL);
t.tv_sec = now.tv_sec + (ms_timeout / 1000) + (total_ns / 1000000000LL);
t.tv_nsec = total_ns % 1000000000LL;

m_mutex.lock();
if (m_size <= 0)
{
t.tv_sec = now.tv_sec + ms_timeout / 1000;
t.tv_nsec = (ms_timeout % 1000) * 1000;
if (!m_cond.timewait(m_mutex.get(), t))
{

// 用 while 对抗虚假唤醒
while (m_size <= 0) {
// check: 直接退出返回
if (m_close) {
m_mutex.unlock();
return false;
}
// timewait 内部是用绝对时间比较的，所以 t 算好一次就可以一直用
if (!m_cond.timewait(m_mutex.get(), t)) {
m_mutex.unlock();
return false; // 真正超时
}
}

if (m_size <= 0)
{
// check：从 timewait 醒来后，可能资源已被析构，必须再次判断
if (m_close) {
m_mutex.unlock();
return false;
}
Expand All @@ -207,6 +243,7 @@ class block_queue
int m_max_size;
int m_front;
int m_back;
bool m_close;
};

#endif