[gcc r12-11182] libatomic: Fix up libat_{, un}lock_n for mingw [PR119796]

[Jakub Jelinek via Gcc-cvs]

https://gcc.gnu.org/g:b22c39bb9bd687fca05d590102b62e0acc88cacf

commit r12-11182-gb22c39bb9bd687fca05d590102b62e0acc88cacf
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.
    
    (cherry picked from commit 34fe8e90007afbc87941df9b01ffcf8747c11497)

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 6efa42cea739..f29186f73a67 100644
--- a/libatomic/config/mingw/lock.c
+++ b/libatomic/config/mingw/lock.c
@@ -86,21 +86,30 @@ 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
@@ -108,17 +117,22 @@ 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);
 }