From: Michael Knyszek <mknyszek@google.com>
Date: Fri, 24 Jan 2020 16:50:53 +0000 (+0000)
Subject: Revert "runtime: release worldsema before Gosched in STW GC mode"
X-Git-Tag: go1.14rc1~68
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ad3cef184e55ab53306a466bda100dc72c40fc3b;p=gostls13.git

Revert "runtime: release worldsema before Gosched in STW GC mode"

This reverts commit 05511a5c0ae238325c10b0e4e44c3f66f928e4cf, CL 208379.

Reason for revert: So that we can cleanly revert
https://golang.org/cl/182657.

Change-Id: I4fdf4f864a093db7866b3306f0f8f856b9f4d684
Reviewed-on: https://go-review.googlesource.com/c/go/+/216357
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
---

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index bda8eadc9d..0bc5568442 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1368,13 +1368,6 @@ func gcStart(trigger gcTrigger) {
 		work.pauseNS += now - work.pauseStart
 		work.tMark = now
 	})
-
-	// Release the world sema before Gosched() in STW mode
-	// because we will need to reacquire it later but before
-	// this goroutine becomes runnable again, and we could
-	// self-deadlock otherwise.
-	semrelease(&worldsema)
-
 	// In STW mode, we could block the instant systemstack
 	// returns, so don't do anything important here. Make sure we
 	// block rather than returning to user code.
@@ -1382,6 +1375,7 @@ func gcStart(trigger gcTrigger) {
 		Gosched()
 	}
 
+	semrelease(&worldsema)
 	semrelease(&work.startSema)
 }