From b25a2d573ac9e7594b5235c81c9f4bc002c7727f Mon Sep 17 00:00:00 2001
From: Mahdi Ali-Raihan <asder8215@gmail.com>
Date: Sat, 21 Mar 2026 13:43:22 -0400
Subject: [PATCH] Prevent no_threads RwLock's write() impl from setting mode to
 -1 when it is locked for reading

---
 library/std/src/sys/sync/rwlock/no_threads.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/library/std/src/sys/sync/rwlock/no_threads.rs b/library/std/src/sys/sync/rwlock/no_threads.rs
index 573d0d602dbd6..6b919bde80bb5 100644
--- a/library/std/src/sys/sync/rwlock/no_threads.rs
+++ b/library/std/src/sys/sync/rwlock/no_threads.rs
@@ -37,8 +37,10 @@ impl RwLock {
 
     #[inline]
     pub fn write(&self) {
-        if self.mode.replace(-1) != 0 {
-            rtabort!("rwlock locked for reading")
+        if self.mode.get() == 0 {
+            self.mode.set(-1);
+        } else {
+            rtabort!("rwlock locked for reading");
         }
     }