From ec972f2878a9c97720ea44ddecf9974e0e691ec8 Mon Sep 17 00:00:00 2001
From: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Date: Mon, 11 Dec 2023 14:16:02 -0300
Subject: [PATCH] iter: fix race instrumentation in Pull2

Pull2 tests are failing with -race, giving false-positive race conditions due to
bad race instrumentation.

No tests for this as it should be caught by the race builders. The only reason
it was not caught is because it is behind GOEXPERIMENT=rangefunc.

Fixes [reserved]
---
 src/iter/iter.go | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/iter/iter.go b/src/iter/iter.go
index 240df00f7f..e89a838ac4 100644
--- a/src/iter/iter.go
+++ b/src/iter/iter.go
@@ -122,18 +122,22 @@ func Pull[V any](seq Seq[V]) (next func() (V, bool), stop func()) {
 // simultaneously.
 func Pull2[K, V any](seq Seq2[K, V]) (next func() (K, V, bool), stop func()) {
 	var (
-		k    K
-		v    V
-		ok   bool
-		done bool
+		k     K
+		v     V
+		ok    bool
+		done  bool
+		racer int
 	)
 	c := newcoro(func(c *coro) {
+		race.Acquire(unsafe.Pointer(&racer))
 		yield := func(k1 K, v1 V) bool {
 			if done {
 				return false
 			}
 			k, v, ok = k1, v1, true
+			race.Release(unsafe.Pointer(&racer))
 			coroswitch(c)
+			race.Acquire(unsafe.Pointer(&racer))
 			return !done
 		}
 		seq(yield)
@@ -141,20 +145,25 @@ func Pull2[K, V any](seq Seq2[K, V]) (next func() (K, V, bool), stop func()) {
 		var v0 V
 		k, v, ok = k0, v0, false
 		done = true
+		race.Release(unsafe.Pointer(&racer))
 	})
 	next = func() (k1 K, v1 V, ok1 bool) {
-		race.Write(unsafe.Pointer(&c)) // detect races
+		race.Write(unsafe.Pointer(&racer)) // detect races
 		if done {
 			return
 		}
+		race.Release(unsafe.Pointer(&racer))
 		coroswitch(c)
+		race.Acquire(unsafe.Pointer(&racer))
 		return k, v, ok
 	}
 	stop = func() {
-		race.Write(unsafe.Pointer(&c)) // detect races
+		race.Write(unsafe.Pointer(&racer)) // detect races
 		if !done {
 			done = true
+			race.Release(unsafe.Pointer(&racer))
 			coroswitch(c)
+			race.Acquire(unsafe.Pointer(&racer))
 		}
 	}
 	return next, stop