这是一个错误。我已经能够通过在task_io_service::do_poll_one
的非关键部分添加延迟来复制它。以下是booost/asio/detail/impl/task_io_service.ipp
中修改的task_io_service::do_poll_one()
的片段。唯一添加的是睡眠。
std::size_t task_io_service::do_poll_one(mutex::scoped_lock& lock,
task_io_service::thread_info& this_thread,
const boost::system::error_code& ec)
{
if (stopped_)
return 0;
operation* o = op_queue_.front();
if (o == &task_operation_)
{
op_queue_.pop();
lock.unlock();
{
task_cleanup c = { this, &lock, &this_thread };
(void)c;
// Run the task. May throw an exception. Only block if the operation
// queue is empty and we're not polling, otherwise we want to return
// as soon as possible.
task_->run(false, this_thread.private_op_queue);
boost::this_thread::sleep_for(boost::chrono::seconds(3));
}
o = op_queue_.front();
if (o == &task_operation_)
return 0;
}
...
我的测试驱动程序是相当基本的:“”
- 通过一个计时器,将打印的异步工作循环每3秒钟一次。
- 产生一个将轮询
io_service
的单个线程。
- 延迟允许新的线程时间轮询
io_service
,并有主要电话io_service::run()
而轮询线程睡在task_io_service::do_poll_one()
。
测试代码:
#include <iostream>
#include <boost/asio/io_service.hpp>
#include <boost/asio/steady_timer.hpp>
#include <boost/chrono.hpp>
#include <boost/thread.hpp>
boost::asio::io_service io_service;
boost::asio::steady_timer timer(io_service);
void arm_timer()
{
std::cout << ".";
std::cout.flush();
timer.expires_from_now(boost::chrono::seconds(3));
timer.async_wait(boost::bind(&arm_timer));
}
int main()
{
// Add asynchronous work loop.
arm_timer();
// Spawn poll thread.
boost::thread poll_thread(
boost::bind(&boost::asio::io_service::poll, boost::ref(io_service)));
// Give time for poll thread service reactor.
boost::this_thread::sleep_for(boost::chrono::seconds(1));
io_service.run();
}
和Debug:
[[email protected] bug]$ gdb a.out
...
(gdb) r
Starting program: /home/twsansbury/dev/bug/a.out
[Thread debugging using libthread_db enabled]
.[New Thread 0xb7feeb90 (LWP 31892)]
[Thread 0xb7feeb90 (LWP 31892) exited]
在这一点上,arm_timer()
已打印 “”一次(当它是武装时)。轮询螺纹以非阻塞的方式为反应堆提供服务,并且睡眠3秒,而op_queue_
为空(将在task_cleanup c
退出范围时被添加回op_queue_
)。 op_queue_
是空的,主线程调用io_service::run()
,看到op_queue_
是空的,并且自己成为first_idle_thread_
,它在wakeup_event
上等待。轮询线程完成睡眠,并返回0
,使主线程等待wakeup_event
。
等待10〜秒,充足的时间为arm_timer()
要准备好后,我中断调试器:
Program received signal SIGINT, Interrupt.
0x00919402 in __kernel_vsyscall()
(gdb) bt
#0 0x00919402 in __kernel_vsyscall()
#1 0x0081bbc5 in [email protected]@GLIBC_2.3.2() from /lib/libpthread.so.0
#2 0x00763b3d in [email protected]@GLIBC_2.3.2() from /lib/libc.so.6
#3 0x08059dc2 in void boost::asio::detail::posix_event::wait >(boost::asio::detail::scoped_lock&)()
#4 0x0805a009 in boost::asio::detail::task_io_service::do_run_one(boost::asio::detail::scoped_lock&, boost::asio::detail::task_io_service_thread_info&, boost::system::error_code const&)()
#5 0x0805a11c in boost::asio::detail::task_io_service::run(boost::system::error_code&)()
#6 0x0805a1e2 in boost::asio::io_service::run()()
#7 0x0804db78 in main()
侧由端的时间表如下:
poll thread | main thread
---------------------------------------+---------------------------------------
lock() |
do_poll_one() |
|-- pop task_operation_ from |
| queue_op_ |
|-- unlock() | lock()
|-- create task_cleanup | do_run_one()
|-- service reactor (non-block) | `-- queue_op_ is empty
|-- ~task_cleanup() | |-- set thread as idle
| |-- lock() | `-- unlock()
| `-- queue_op_.push( |
| task_operation_) |
`-- task_operation_ is |
queue_op_.front() |
`-- return 0 | // still waiting on wakeup_event
unlock() |
尽我所知,没有修补的副作用:
if (o == &task_operation_)
return 0;
到:
if (o == &task_operation_)
{
if (!one_thread_)
wake_one_thread_and_unlock(lock);
return 0;
}
无论如何,我已经提交了bug and fix。考虑留意官方回应的机票。
run_one()返回的代码是什么? –
如果它返回1是正常的,只有当它返回0时才需要重置io_service。这听起来不像你做错任何事情,你可以发布sscce吗? –
@DavidSchwartz你确定pthread_cond_timedwait调用来自asio吗?我在代码中遇到了一些麻烦。 – janm