英文:
How does Go preempt goroutines in windows?
问题
我读到了goroutine现在是可抢占的。抢占是通过一个名为sysmon的goroutine发送停止信号给已经用完时间片的goroutine来实现的。在posix系统上，我相信这是通过pthread_kill来完成的。我的问题是：在Windows上如何实现这个功能，因为Windows不支持线程信号？我曾经以为Go运行时可能使用了一个类似pthreads4w的posix线程库，然而我刚刚看到，即使在pthreads4w中，pthread_kill也不支持发送信号。
英文:
I read that goroutines are now preemptible. The preemption is done via a sysmon goroutine that sends stop signals to goroutines which have used up their time slice. On posix systems, I believe this is done through pthread_kill. My question is: how does this work in windows since windows doesn't support thread signaling? I had assumed that the go runtime may have been using a posix thread library like pthreads4w, however I just saw that even in pthreads4w, pthread_kill doesn't support sending signals.
答案1
得分: 1
runtime/preempt.go中的注释概述了运行时中异步抢占的工作原理。特别是与异步抢占相关的部分：
> 在异步安全点进行的抢占是通过使用操作系统机制（例如信号）来暂停线程，并检查其状态以确定goroutine是否在异步安全点。
那么在Windows上如何实现异步抢占呢？正如在原始的提案中提到的非协作式goroutine抢占：
> ### 其他考虑因素
> ... 在Windows上支持信号抢占非常容易，因为它提供了SuspendThread和GetThreadContext...
Windows的SuspendThread函数可以通过线程句柄来暂停线程，GetThreadContext函数可以获取线程的处理器状态。这些函数的具体用法在runtime/os_windows.go中实现。
英文:
The comments in runtime/preempt.go give an overview of how preemption works in the runtime. Specifically to do with asynchronous preemption:
> Preemption at asynchronous safe-points is implemented by suspending the thread using an OS mechanism (e.g., signals) and inspecting its state to determine if the goroutine was at an asynchronous safe-point.
So how does async preemption work on windows? As mentioned in the original proposal for non-cooperative preemption of goroutines:
> ### Other considerations
> ... signaled preemption is quite easy to support in Windows because it provides SuspendThread and GetThreadContext ...
The Windows SuspendThread function can be used to suspend a thread by its handle, and GetThreadContext can be used to get the processor state of the thread. The specific usages of these functions are implemented in runtime/os_windows.go
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