From: Andy Pan <i@andypan.me>
Date: Wed, 5 Mar 2025 08:14:42 +0000 (+0800)
Subject: [release-branch.go1.24] runtime: explicitly disable async preempt for internal/runtime
X-Git-Tag: go1.24.2~4
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=0ae3ca0a20db5f9df978fa59cd0e8751ac9f5250;p=gostls13.git

[release-branch.go1.24] runtime: explicitly disable async preempt for internal/runtime

Fixes #72115
For #71591
Relevant CL 560155

Change-Id: Iebc497d56b36d50c13a6dd88e7bca4578a03cf63
Reviewed-on: https://go-review.googlesource.com/c/go/+/654916
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
(cherry picked from commit 92a63bdfee9f8347df70293e5733661ae31ae285)
Reviewed-on: https://go-review.googlesource.com/c/go/+/660857
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>
---

diff --git a/src/cmd/internal/objabi/pkgspecial.go b/src/cmd/internal/objabi/pkgspecial.go
index 9828e12281..871c28f588 100644
--- a/src/cmd/internal/objabi/pkgspecial.go
+++ b/src/cmd/internal/objabi/pkgspecial.go
@@ -43,6 +43,9 @@ type PkgSpecial struct {
 }
 
 var runtimePkgs = []string{
+	// TODO(panjf2000): consider syncing the list inside the
+	// 	isAsyncSafePoint in preempt.go based on this list?
+
 	"runtime",
 
 	"internal/runtime/atomic",
diff --git a/src/runtime/preempt.go b/src/runtime/preempt.go
index 45b1b5e9c7..839f3875be 100644
--- a/src/runtime/preempt.go
+++ b/src/runtime/preempt.go
@@ -419,14 +419,21 @@ func isAsyncSafePoint(gp *g, pc, sp, lr uintptr) (bool, uintptr) {
 	name := u.srcFunc(uf).name()
 	if stringslite.HasPrefix(name, "runtime.") ||
 		stringslite.HasPrefix(name, "runtime/internal/") ||
+		stringslite.HasPrefix(name, "internal/runtime/") ||
 		stringslite.HasPrefix(name, "reflect.") {
 		// For now we never async preempt the runtime or
 		// anything closely tied to the runtime. Known issues
 		// include: various points in the scheduler ("don't
 		// preempt between here and here"), much of the defer
 		// implementation (untyped info on stack), bulk write
-		// barriers (write barrier check),
-		// reflect.{makeFuncStub,methodValueCall}.
+		// barriers (write barrier check), atomic functions in
+		// internal/runtime/atomic, reflect.{makeFuncStub,methodValueCall}.
+		//
+		// Note that this is a subset of the runtimePkgs in pkgspecial.go
+		// and these checks are theoretically redundant because the compiler
+		// marks "all points" in runtime functions as unsafe for async preemption.
+		// But for some reason, we can't eliminate these checks until https://go.dev/issue/72031
+		// is resolved.
 		//
 		// TODO(austin): We should improve this, or opt things
 		// in incrementally.