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7adcbafe | 1 | /* Copyright (C) 2012-2022 Free Software Foundation, Inc. |
48310492 RH |
2 | Contributed by Richard Henderson <rth@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 | #include "libatomic_i.h" | |
26 | #include <pthread.h> | |
27 | ||
28 | ||
29 | /* The target page size. Must be no larger than the runtime page size, | |
30 | lest locking fail with virtual address aliasing (i.e. a page mmaped | |
31 | at two locations). */ | |
32 | #ifndef PAGE_SIZE | |
33 | #define PAGE_SIZE 4096 | |
34 | #endif | |
35 | ||
36 | /* The target cacheline size. This is an optimization; the padding that | |
37 | should be applied to the locks to keep them from interfering. */ | |
38 | #ifndef CACHLINE_SIZE | |
39 | #define CACHLINE_SIZE 64 | |
40 | #endif | |
41 | ||
42 | /* The granularity at which locks are applied. Almost certainly the | |
43 | cachline size is the right thing to use here. */ | |
44 | #ifndef WATCH_SIZE | |
45 | #define WATCH_SIZE CACHLINE_SIZE | |
46 | #endif | |
47 | ||
48 | struct lock | |
49 | { | |
50 | pthread_mutex_t mutex; | |
51 | char pad[sizeof(pthread_mutex_t) < CACHLINE_SIZE | |
52 | ? CACHLINE_SIZE - sizeof(pthread_mutex_t) | |
53 | : 0]; | |
54 | }; | |
55 | ||
56 | #define NLOCKS (PAGE_SIZE / WATCH_SIZE) | |
57 | static struct lock locks[NLOCKS] = { | |
58 | [0 ... NLOCKS-1].mutex = PTHREAD_MUTEX_INITIALIZER | |
59 | }; | |
60 | ||
61 | static inline uintptr_t | |
62 | addr_hash (void *ptr) | |
63 | { | |
64 | return ((uintptr_t)ptr / WATCH_SIZE) % NLOCKS; | |
65 | } | |
66 | ||
67 | void | |
68 | libat_lock_1 (void *ptr) | |
69 | { | |
70 | pthread_mutex_lock (&locks[addr_hash (ptr)].mutex); | |
71 | } | |
72 | ||
73 | void | |
74 | libat_unlock_1 (void *ptr) | |
75 | { | |
76 | pthread_mutex_unlock (&locks[addr_hash (ptr)].mutex); | |
77 | } | |
78 | ||
79 | void | |
80 | libat_lock_n (void *ptr, size_t n) | |
81 | { | |
82 | uintptr_t h = addr_hash (ptr); | |
83 | size_t i = 0; | |
84 | ||
85 | /* Don't lock more than all the locks we have. */ | |
86 | if (n > PAGE_SIZE) | |
87 | n = PAGE_SIZE; | |
88 | ||
89 | do | |
90 | { | |
91 | pthread_mutex_lock (&locks[h].mutex); | |
92 | if (++h == NLOCKS) | |
93 | h = 0; | |
94 | i += WATCH_SIZE; | |
95 | } | |
96 | while (i < n); | |
97 | } | |
98 | ||
99 | void | |
100 | libat_unlock_n (void *ptr, size_t n) | |
101 | { | |
102 | uintptr_t h = addr_hash (ptr); | |
103 | size_t i = 0; | |
104 | ||
105 | if (n > PAGE_SIZE) | |
106 | n = PAGE_SIZE; | |
107 | ||
108 | do | |
109 | { | |
110 | pthread_mutex_unlock (&locks[h].mutex); | |
111 | if (++h == NLOCKS) | |
112 | h = 0; | |
113 | i += WATCH_SIZE; | |
114 | } | |
115 | while (i < n); | |
116 | } |