From 62a4359e2e479dc7392b645faecf7cdc5ff4cda0 Mon Sep 17 00:00:00 2001
From: Rick Hudson <rlh@golang.org>
Date: Thu, 23 Oct 2014 15:51:17 -0400
Subject: [PATCH] [dev.garbage] runtime: simplifiy lfstack.c due to undiagnosed
 buffer corruption. The changes got rid of the problems we were seeing. We
 suspect the pushcnt field has a race.

LGTM=rsc
R=dvyukov, rsc
CC=golang-codereviews
https://golang.org/cl/159330043
---
 src/runtime/lfstack.c | 14 ++++++--------
 src/runtime/runtime.h |  2 +-
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/src/runtime/lfstack.c b/src/runtime/lfstack.c
index 57e0af2829..0ced839c23 100644
--- a/src/runtime/lfstack.c
+++ b/src/runtime/lfstack.c
@@ -46,7 +46,7 @@ runtime·lfstackpush(uint64 *head, LFNode *node)
 	new = (uint64)(uintptr)node|(((uint64)node->pushcnt&CNT_MASK)<<PTR_BITS);
 	for(;;) {
 		old = runtime·atomicload64(head);
-		node->next = (LFNode*)(uintptr)(old&PTR_MASK);
+		node->next = old;
 		if(runtime·cas64(head, old, new))
 			break;
 	}
@@ -55,19 +55,17 @@ runtime·lfstackpush(uint64 *head, LFNode *node)
 LFNode*
 runtime·lfstackpop(uint64 *head)
 {
-	LFNode *node, *node2;
-	uint64 old, new;
+	LFNode *node;
+	uint64 old, next;
 
 	for(;;) {
 		old = runtime·atomicload64(head);
 		if(old == 0)
 			return nil;
 		node = (LFNode*)(uintptr)(old&PTR_MASK);
-		node2 = runtime·atomicloadp(&node->next);
-		new = 0;
-		if(node2 != nil)
-			new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt&CNT_MASK)<<PTR_BITS);
-		if(runtime·cas64(head, old, new))
+		next = runtime·atomicload64(&node->next);
+
+		if(runtime·cas64(head, old, next))
 			return node;
 	}
 }
diff --git a/src/runtime/runtime.h b/src/runtime/runtime.h
index bea7737993..37929c59cf 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -573,7 +573,7 @@ enum {
 // Lock-free stack node.
 struct LFNode
 {
-	LFNode	*next;
+	uint64	next;
 	uintptr	pushcnt;
 };
 
-- 
2.48.1