From 584b062a302ca10ecab4488a473440db7173bb2a Mon Sep 17 00:00:00 2001
From: Jim Price <shadeops@gmail.com>
Date: Wed, 26 Jul 2023 06:19:52 -0700
Subject: [PATCH] Fix counting in SingleThreadedRwLock's tryLockShared (#16560)

Additionally we add RwLock to Thread.zig's list of tests
---
 lib/std/Thread.zig        | 1 +
 lib/std/Thread/RwLock.zig | 6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/std/Thread.zig b/lib/std/Thread.zig
index 99e2feb4cf..64815bde72 100644
--- a/lib/std/Thread.zig
+++ b/lib/std/Thread.zig
@@ -1438,6 +1438,7 @@ test {
     _ = Mutex;
     _ = Semaphore;
     _ = Condition;
+    _ = RwLock;
 }
 
 fn testIncrementNotify(value: *usize, event: *ResetEvent) void {
diff --git a/lib/std/Thread/RwLock.zig b/lib/std/Thread/RwLock.zig
index e78695a1d8..e77db10abb 100644
--- a/lib/std/Thread/RwLock.zig
+++ b/lib/std/Thread/RwLock.zig
@@ -95,7 +95,11 @@ pub const SingleThreadedRwLock = struct {
                 rwl.shared_count = 1;
                 return true;
             },
-            .locked_exclusive, .locked_shared => return false,
+            .locked_shared => {
+                rwl.shared_count += 1;
+                return true;
+            },
+            .locked_exclusive => return false,
         }
     }