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
addr_hash(void * ptr)64 addr_hash (void *ptr)
65 {
66 return ((uintptr_t)ptr / WATCH_SIZE) % NLOCKS;
67 }
68
69 void
libat_lock_1(void * ptr)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
libat_unlock_1(void * ptr)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
libat_lock_n(void * ptr,size_t n)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
libat_unlock_n(void * ptr,size_t n)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 }
125