libatomic/config/mingw/lock.c

   1 /* Copyright (C) 2014-2020 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 #include <windows.h>
  27 #undef UWORD
  28 #include "libatomic_i.h"
  29
  30 /* The target page size.  Must be no larger than the runtime page size,
  31    lest locking fail with virtual address aliasing (i.e. a page mmaped
  32    at two locations).  */
  33 #ifndef PAGE_SIZE
  34 #define PAGE_SIZE 4096
  35 #endif
  36
  37 /* The target cacheline size.  This is an optimization; the padding that
  38    should be applied to the locks to keep them from interfering.  */
  39 #ifndef CACHLINE_SIZE
  40 #define CACHLINE_SIZE 64
  41 #endif
  42
  43 /* The granularity at which locks are applied.  Almost certainly the
  44    cachline size is the right thing to use here.  */
  45 #ifndef WATCH_SIZE
  46 #define WATCH_SIZE CACHLINE_SIZE
  47 #endif
  48
  49 struct lock
  50 {
  51   HANDLE mutex;
  52   char pad[sizeof (HANDLE) < CACHLINE_SIZE
  53            ? CACHLINE_SIZE - sizeof (HANDLE)
  54            : 0];
  55 };
  56
  57 #define NLOCKS (PAGE_SIZE / WATCH_SIZE)
  58
  59 static struct lock locks[NLOCKS] = {
  60   [0 ... NLOCKS-1].mutex = NULL
  61 };
  62
  63 static inline uintptr_t
  64 addr_hash (void *ptr)
  65 {
  66   return ((uintptr_t)ptr / WATCH_SIZE) % NLOCKS;
  67 }
  68
  69 void
  70 libat_lock_1 (void *ptr)
  71 {
  72   if (!locks[addr_hash (ptr)].mutex)
  73     locks[addr_hash (ptr)].mutex = CreateMutex  (NULL, FALSE, NULL);
  74   WaitForSingleObject (locks[addr_hash (ptr)].mutex, INFINITE);
  75 }
  76
  77 void
  78 libat_unlock_1 (void *ptr)
  79 {
  80   if (locks[addr_hash (ptr)].mutex)
  81     ReleaseMutex (locks[addr_hash (ptr)].mutex);
  82 }
  83
  84 void
  85 libat_lock_n (void *ptr, size_t n)
  86 {
  87   uintptr_t h = addr_hash (ptr);
  88   size_t i = 0;
  89
  90   /* Don't lock more than all the locks we have.  */
  91   if (n > PAGE_SIZE)
  92     n = PAGE_SIZE;
  93
  94   do
  95     {
  96       if (!locks[h].mutex)
  97         locks[h].mutex = CreateMutex  (NULL, FALSE, NULL);
  98       WaitForSingleObject (locks[h].mutex, INFINITE);
  99       if (++h == NLOCKS)
 100         h = 0;
 101       i += WATCH_SIZE;
 102     }
 103   while (i < n);
 104 }
 105
 106 void
 107 libat_unlock_n (void *ptr, size_t n)
 108 {
 109   uintptr_t h = addr_hash (ptr);
 110   size_t i = 0;
 111
 112   if (n > PAGE_SIZE)
 113     n = PAGE_SIZE;
 114
 115   do
 116     {
 117       if (locks[h].mutex)
 118         ReleaseMutex (locks[h].mutex);
 119       if (++h == NLOCKS)
 120         h = 0;
 121       i += WATCH_SIZE;
 122     }
 123   while (i < n);
 124 }