[gcc r15-9526] libatomic: Fix up libat_{, un}lock_n for mingw [PR119796]

[Jakub Jelinek via Gcc-cvs]

https://gcc.gnu.org/g:34fe8e90007afbc87941df9b01ffcf8747c11497

commit r15-9526-g34fe8e90007afbc87941df9b01ffcf8747c11497
Author: Jakub Jelinek <ja...@redhat.com>
Date:   Wed Apr 16 17:22:49 2025 +0200

    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  <ja...@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.

Diff:
---
 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 17faa66547d6..8b0b4ddfdd0b 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);
 }