utopia9527 commented on issue #2736:
URL: https://github.com/apache/brpc/issues/2736#issuecomment-2286450670
> 可以用gdb看看worker线程都卡在哪
都卡在了 bthread 池子的加锁处。 当把锁和条件变量都换成 std 之后不会发生这种问题。 有如下怀疑死锁的原因，辛苦大佬帮忙看看：
bthread 池子中，往公共队列读写都会加bthread 锁。 有没有可能 同一个worker
调度了多个池子中的bthread，多次加锁，导致死锁的发生。
调试信息
```
#0 0x00007f2309b6952d in syscall () from /lib64/libc.so.6
#1 0x00007f230a491841 in
std::__atomic_futex_unsigned_base::_M_futex_wait_until(unsigned int*, unsigned
int, bool, std::chrono::duration<long, std::ratio<1l, 1l> >,
std::chrono::duration<long, std::ratio<1l, 1000000000l> >) () from
/lib64/libstdc++.so.6
#2 0x00000000004be95e in
std::__atomic_futex_unsigned<2147483648u>::_M_load_and_test_until
(this=0x7f22d05cb020, __assumed=0, __operand=1, __equal=true,
__mo=std::memory_order_acquire, __has_timeout=false, __s=..., __ns=...) at
/usr/include/c++/8/bits/atomic_futex.h:102
#3 0x00000000004aee85 in
std::__atomic_futex_unsigned<2147483648u>::_M_load_and_test
(this=0x7f22d05cb020, __assumed=0, __operand=1, __equal=true,
__mo=std::memory_order_acquire) at /usr/include/c++/8/bits/atomic_futex.h:122
#4 0x000000000048f2c1 in
std::__atomic_futex_unsigned<2147483648u>::_M_load_when_equal
(__mo=std::memory_order_acquire, __val=1, this=0x7f22d05cb020) at
/usr/include/c++/8/bits/atomic_futex.h:162
#5 std::__future_base::_State_baseV2::wait (this=0x7f22d05cb010) at
/usr/include/c++/8/future:337
#6 0x00000000005a3577 in
std::__basic_future<std::vector<std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >,
std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> > > > >::_M_get_result (this=0x7f22d0028b80) at
/usr/include/c++/8/future:717
#7 0x00000000005a272a in
std::future<std::vector<std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >,
std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> > > > >::get (this=0x7f22d0028b80) at
/usr/include/c++/8/future:796
```
代码
```
// 往池子里加任务
template <class F, class... Args>
auto BThreadPool::enqueue(F&& f, Args&&... args)
-> std::future<typename std::invoke_result<F, Args...>::type> {
using return_type = typename std::invoke_result<F, Args...>::type;
auto task = std::make_shared<std::packaged_task<return_type()>>(
std::bind(std::forward<F>(f), std::forward<Args>(args)...));
std::future<return_type> res = task->get_future();
{
std::lock_guard<bthread_mutex_t> lock(queue_mutex_);
if (stop_) throw std::runtime_error("enqueue on stop_ped ThreadPool");
tasks.emplace([task]() { (*task)(); });
}
bthread_cond_signal(&condition_);
return res;
}
// 从池子取出任务
void* BThreadPool::TaskFunction(void* args) {
auto* tp = reinterpret_cast<BThreadPool*>(args);
while (true) {
std::function<void()> task;
{
// Already specialize "std::lock_guard" and "std::unique_lock" for
// bthread_mutex_t
std::lock_guard<bthread_mutex_t> lock(tp->queue_mutex_);
while (tp->tasks.empty()) {
if (tp->stop_) break;
bthread_cond_wait(&tp->condition_, &tp->queue_mutex_);
}
if (tp->stop_ && tp->tasks.empty()) {
return nullptr;
}
task = std::move(tp->tasks.front());
tp->tasks.pop();
}
task();
}
}
```
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