From 68fc92110539402daf4a70c450ac28be7fb3e04d Mon Sep 17 00:00:00 2001
From: Antonis Geralis <43617260+planetis-m@users.noreply.github.com>
Date: Wed, 8 Dec 2021 10:34:45 +0200
Subject: [PATCH 1/2] fix atomics memory ordering for sharedptr

Consume was used in the original pr https://github.com/nim-lang/Nim/pull/10485, haven't questioned before https://github.com/nim-lang/Nim/pull/19212
---
 threading/smartptrs.nim | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/threading/smartptrs.nim b/threading/smartptrs.nim
index 25480b7..c6aebe1 100644
--- a/threading/smartptrs.nim
+++ b/threading/smartptrs.nim
@@ -81,15 +81,13 @@ type
 
 proc `=destroy`*[T](p: var SharedPtr[T]) =
   if p.val != nil:
-    if p.val[].counter.load(Consume) == 0:
+    if fetchSub(p.val[].counter, 1, AcqRel) == 0:
       `=destroy`(p.val[])
       deallocShared(p.val)
-    else:
-      atomicDec(p.val[].counter)
 
 proc `=copy`*[T](dest: var SharedPtr[T], src: SharedPtr[T]) =
   if src.val != nil:
-    atomicInc(src.val[].counter)
+    discard fetchAdd(src.val[].counter, 1, Relaxed)
   if dest.val != nil:
     `=destroy`(dest)
   dest.val = src.val

From 3f605ce300dbc2563ddaf22426a3162fbdd78389 Mon Sep 17 00:00:00 2001
From: Antonis Geralis <43617260+planetis-m@users.noreply.github.com>
Date: Fri, 10 Dec 2021 19:37:33 +0200
Subject: [PATCH 2/2] Prefer the original logic over simplification

---
 threading/smartptrs.nim | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/threading/smartptrs.nim b/threading/smartptrs.nim
index c6aebe1..ab579a5 100644
--- a/threading/smartptrs.nim
+++ b/threading/smartptrs.nim
@@ -81,9 +81,11 @@ type
 
 proc `=destroy`*[T](p: var SharedPtr[T]) =
   if p.val != nil:
-    if fetchSub(p.val[].counter, 1, AcqRel) == 0:
+    if p.val[].counter.load(Acquire) == 0:
       `=destroy`(p.val[])
       deallocShared(p.val)
+    else:
+      discard fetchSub(p.val[].counter, 1, Release)
 
 proc `=copy`*[T](dest: var SharedPtr[T], src: SharedPtr[T]) =
   if src.val != nil: