On Mon, 14 Apr 2025, Jakub Jelinek wrote:
> Hi!
>
> Here is just a port of the previously posted patch to mingw which
> clearly has the same problems.
>
> Untested though, I don't have Windows anywhere around.
OK.
Richard.
> 2025-04-14 Jakub Jelinek <ja...@redhat.com>
>
> PR libstdc++/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.jj 2025-04-08 14:09:40.988589457 +0200
> +++ libatomic/config/mingw/lock.c 2025-04-14 15:39:08.244686172 +0200
> @@ -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);
> }
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
