1  /* Copyright (C) 2014-2023 Free Software Foundation, Inc.
       2     Contributed by Kai Tietz <ktietz@redhat.com>.
       3  
       4     This file is part of the GNU Atomic Library (libatomic).
       5  
       6     Libatomic is free software; you can redistribute it and/or modify it
       7     under the terms of the GNU General Public License as published by
       8     the Free Software Foundation; either version 3 of the License, or
       9     (at your option) any later version.
      10  
      11     Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
      12     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
      13     FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
      14     more details.
      15  
      16     Under Section 7 of GPL version 3, you are granted additional
      17     permissions described in the GCC Runtime Library Exception, version
      18     3.1, as published by the Free Software Foundation.
      19  
      20     You should have received a copy of the GNU General Public License and
      21     a copy of the GCC Runtime Library Exception along with this program;
      22     see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23     <http://www.gnu.org/licenses/>.  */
      24  
      25  #define UWORD __shadow_UWORD
      26  #define WIN32_LEAN_AND_MEAN
      27  #include <windows.h>
      28  #undef UWORD
      29  #include "libatomic_i.h"
      30  
      31  /* The target page size.  Must be no larger than the runtime page size,
      32     lest locking fail with virtual address aliasing (i.e. a page mmaped
      33     at two locations).  */
      34  #ifndef PAGE_SIZE
      35  #define PAGE_SIZE 4096
      36  #endif
      37  
      38  /* The target cacheline size.  This is an optimization; the padding that
      39     should be applied to the locks to keep them from interfering.  */
      40  #ifndef CACHLINE_SIZE
      41  #define CACHLINE_SIZE 64
      42  #endif
      43  
      44  /* The granularity at which locks are applied.  Almost certainly the
      45     cachline size is the right thing to use here.  */
      46  #ifndef WATCH_SIZE
      47  #define WATCH_SIZE CACHLINE_SIZE
      48  #endif
      49  
      50  struct lock
      51  {
      52    HANDLE mutex;
      53    char pad[sizeof (HANDLE) < CACHLINE_SIZE
      54  	   ? CACHLINE_SIZE - sizeof (HANDLE)
      55  	   : 0];
      56  };
      57  
      58  #define NLOCKS (PAGE_SIZE / WATCH_SIZE)
      59  
      60  static struct lock locks[NLOCKS] = {
      61    [0 ... NLOCKS-1].mutex = NULL
      62  };
      63  
      64  static inline uintptr_t 
      65  addr_hash (void *ptr)
      66  {
      67    return ((uintptr_t)ptr / WATCH_SIZE) % NLOCKS;
      68  }
      69  
      70  void
      71  libat_lock_1 (void *ptr)
      72  {
      73    if (!locks[addr_hash (ptr)].mutex)
      74      locks[addr_hash (ptr)].mutex = CreateMutex  (NULL, FALSE, NULL);
      75    WaitForSingleObject (locks[addr_hash (ptr)].mutex, INFINITE);
      76  }
      77  
      78  void
      79  libat_unlock_1 (void *ptr)
      80  {
      81    if (locks[addr_hash (ptr)].mutex)
      82      ReleaseMutex (locks[addr_hash (ptr)].mutex);
      83  }
      84  
      85  void
      86  libat_lock_n (void *ptr, size_t n)
      87  {
      88    uintptr_t h = addr_hash (ptr);
      89    size_t i = 0;
      90  
      91    /* Don't lock more than all the locks we have.  */
      92    if (n > PAGE_SIZE)
      93      n = PAGE_SIZE;
      94  
      95    do
      96      {
      97        if (!locks[h].mutex)
      98  	locks[h].mutex = CreateMutex  (NULL, FALSE, NULL);
      99        WaitForSingleObject (locks[h].mutex, INFINITE);
     100        if (++h == NLOCKS)
     101  	h = 0;
     102        i += WATCH_SIZE;
     103      }
     104    while (i < n);
     105  }
     106  
     107  void
     108  libat_unlock_n (void *ptr, size_t n)
     109  {
     110    uintptr_t h = addr_hash (ptr);
     111    size_t i = 0;
     112  
     113    if (n > PAGE_SIZE)
     114      n = PAGE_SIZE;
     115  
     116    do
     117      {
     118        if (locks[h].mutex)
     119  	ReleaseMutex (locks[h].mutex);
     120        if (++h == NLOCKS)
     121  	h = 0;
     122        i += WATCH_SIZE;
     123      }
     124    while (i < n);
     125  }