tree dbe03bd384e2b2cf0ce13dd773a8c269c08612f7
parent 6fd467ee29226bf4b875921b7cb3b692c9db52ef
author Austin Clements <austin@google.com> 1572034661 -0400
committer Austin Clements <austin@google.com> 1574270039 +0000

runtime: support preemption on windows/{386,amd64}

This implements preemptM on Windows using SuspendThead and
ResumeThread.

Unlike on POSIX platforms, preemptM on Windows happens synchronously.
This means we need a make a few other tweaks to suspendG:

1. We need to CAS the G back to _Grunning before doing the preemptM,
   or there's a good chance we'll just catch the G spinning on its
   status in the runtime, which won't be preemptible.

2. We need to rate-limit preemptM attempts. Otherwise, if the first
   attempt catches the G at a non-preemptible point, the busy loop in
   suspendG may hammer it so hard that it never makes it past that
   non-preemptible point.

Updates #10958, #24543.

Change-Id: Ie53b098811096f7e45d864afd292dc9e999ce226
Reviewed-on: https://go-review.googlesource.com/c/go/+/204340
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>