From 34fe8e90007afbc87941df9b01ffcf8747c11497 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 16 Apr 2025 17:22:49 +0200
Subject: [PATCH] libatomic: Fix up libat_{,un}lock_n for mingw [PR119796]

Here is just a port of the previously posted patch to mingw which
clearly has the same problems.

2025-04-16  Jakub Jelinek  <jakub@redhat.com>

	PR libgcc/101075
	PR libgcc/119796
	* config/mingw/lock.c (libat_lock_n, libat_unlock_n): Start with
	computing how many locks will be needed and take into account
	((uintptr_t)ptr % WATCH_SIZE).  If some locks from the end of the
	locks array and others from the start of it will be needed, first
	lock the ones from the start followed by ones from the end.
---
 libatomic/config/mingw/lock.c | 50 ++++++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 18 deletions(-)

diff --git a/libatomic/config/mingw/lock.c b/libatomic/config/mingw/lock.c
index 17faa66547d..8b0b4ddfdd0 100644
--- a/libatomic/config/mingw/lock.c
+++ b/libatomic/config/mingw/lock.c
@@ -87,21 +87,30 @@ libat_lock_n (void *ptr, size_t n)
 {
   uintptr_t h = addr_hash (ptr);
   size_t i = 0;
+  size_t nlocks
+    = (n + ((uintptr_t)ptr % WATCH_SIZE) + WATCH_SIZE - 1) / WATCH_SIZE;
 
   /* Don't lock more than all the locks we have.  */
-  if (n > PAGE_SIZE)
-    n = PAGE_SIZE;
+  if (nlocks > NLOCKS)
+    nlocks = NLOCKS;
 
-  do
+  if (__builtin_expect (h + nlocks > NLOCKS, 0))
+    {
+      size_t j = h + nlocks - NLOCKS;
+      for (; i < j; ++i)
+	{
+	  if (!locks[i].mutex)
+	    locks[i].mutex = CreateMutex (NULL, FALSE, NULL);
+	  WaitForSingleObject (locks[i].mutex, INFINITE);
+	}
+    }
+
+  for (; i < nlocks; ++i)
     {
       if (!locks[h].mutex)
-	locks[h].mutex = CreateMutex  (NULL, FALSE, NULL);
-      WaitForSingleObject (locks[h].mutex, INFINITE);
-      if (++h == NLOCKS)
-	h = 0;
-      i += WATCH_SIZE;
+	locks[h].mutex = CreateMutex (NULL, FALSE, NULL);
+      WaitForSingleObject (locks[h++].mutex, INFINITE);
     }
-  while (i < n);
 }
 
 void
@@ -109,17 +118,22 @@ libat_unlock_n (void *ptr, size_t n)
 {
   uintptr_t h = addr_hash (ptr);
   size_t i = 0;
+  size_t nlocks
+    = (n + ((uintptr_t)ptr % WATCH_SIZE) + WATCH_SIZE - 1) / WATCH_SIZE;
 
-  if (n > PAGE_SIZE)
-    n = PAGE_SIZE;
+  /* Don't lock more than all the locks we have.  */
+  if (nlocks > NLOCKS)
+    nlocks = NLOCKS;
 
-  do
+  if (__builtin_expect (h + nlocks > NLOCKS, 0))
     {
-      if (locks[h].mutex)
-	ReleaseMutex (locks[h].mutex);
-      if (++h == NLOCKS)
-	h = 0;
-      i += WATCH_SIZE;
+      size_t j = h + nlocks - NLOCKS;
+      for (; i < j; ++i)
+	if (locks[i].mutex)
+	  ReleaseMutex (locks[i].mutex);
     }
-  while (i < n);
+
+  for (; i < nlocks; ++i, ++h)
+    if (locks[h].mutex)
+      ReleaseMutex (locks[h].mutex);
 }