1
2 /*--------------------------------------------------------------------*/
3 /*--- Semaphore stuff. sema.c ---*/
4 /*--------------------------------------------------------------------*/
5
6 /*
7 This file is part of Valgrind, a dynamic binary instrumentation
8 framework.
9
10 Copyright (C) 2000-2017 Julian Seward
11 jseward@acm.org
12
13 This program is free software; you can redistribute it and/or
14 modify it under the terms of the GNU General Public License as
15 published by the Free Software Foundation; either version 2 of the
16 License, or (at your option) any later version.
17
18 This program is distributed in the hope that it will be useful, but
19 WITHOUT ANY WARRANTY; without even the implied warranty of
20 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
21 General Public License for more details.
22
23 You should have received a copy of the GNU General Public License
24 along with this program; if not, write to the Free Software
25 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
26 02111-1307, USA.
27
28 The GNU General Public License is contained in the file COPYING.
29 */
30
31 #include "pub_core_basics.h"
32 #include "pub_core_debuglog.h"
33 #include "pub_core_vki.h"
34 #include "pub_core_libcassert.h"
35 #include "pub_core_libcfile.h"
36 #include "pub_core_libcproc.h" // For VG_(gettid)()
37 #include "pub_core_inner.h"
38 #if defined(ENABLE_INNER_CLIENT_REQUEST)
39 #include "helgrind/helgrind.h"
40 #endif
41 #include "priv_sema.h"
42
43 /*
44 Slower (than the removed futex-based sema scheme) but more portable
45 pipe-based token passing scheme.
46 */
47
48 /* Cycle the char passed through the pipe through 'A' .. 'Z' to make
49 it easier to make sense of strace/truss output - makes it possible
50 to see more clearly the change of ownership of the lock. Need to
51 be careful to reinitialise it at fork() time. */
52 static HChar sema_char = '!'; /* will cause assertion failures if used
53 before sema_init */
54
ML_(sema_init)55 void ML_(sema_init)(vg_sema_t *sema)
56 {
57 HChar buf[2];
58 Int res, r;
59 r = VG_(pipe)(sema->pipe);
60 vg_assert(r == 0);
61
62 vg_assert(sema->pipe[0] != sema->pipe[1]);
63
64 sema->pipe[0] = VG_(safe_fd)(sema->pipe[0]);
65 sema->pipe[1] = VG_(safe_fd)(sema->pipe[1]);
66
67 if (0)
68 VG_(debugLog)(0,"zz","sema_init: %d %d\n", sema->pipe[0],
69 sema->pipe[1]);
70 vg_assert(sema->pipe[0] != sema->pipe[1]);
71
72 sema->owner_lwpid = -1;
73
74 /* create initial token */
75 sema_char = 'A';
76 buf[0] = sema_char;
77 buf[1] = 0;
78 sema_char++;
79 INNER_REQUEST(ANNOTATE_RWLOCK_CREATE(sema));
80 INNER_REQUEST(ANNOTATE_BENIGN_RACE_SIZED(&sema->owner_lwpid,
81 sizeof(sema->owner_lwpid), ""));
82 res = VG_(write)(sema->pipe[1], buf, 1);
83 vg_assert(res == 1);
84 }
85
ML_(sema_deinit)86 void ML_(sema_deinit)(vg_sema_t *sema)
87 {
88 vg_assert(sema->owner_lwpid != -1); /* must be initialised */
89 vg_assert(sema->pipe[0] != sema->pipe[1]);
90 INNER_REQUEST(ANNOTATE_RWLOCK_DESTROY(sema));
91 VG_(close)(sema->pipe[0]);
92 VG_(close)(sema->pipe[1]);
93 sema->pipe[0] = sema->pipe[1] = -1;
94 sema->owner_lwpid = -1;
95 }
96
97 /* get a token */
ML_(sema_down)98 void ML_(sema_down)( vg_sema_t *sema, Bool as_LL )
99 {
100 HChar buf[2];
101 Int ret;
102 Int lwpid = VG_(gettid)();
103
104 vg_assert(sema->owner_lwpid != lwpid); /* can't have it already */
105 vg_assert(sema->pipe[0] != sema->pipe[1]);
106
107 again:
108 buf[0] = buf[1] = 0;
109 ret = VG_(read)(sema->pipe[0], buf, 1);
110 INNER_REQUEST(ANNOTATE_RWLOCK_ACQUIRED(sema, /*is_w*/1));
111
112 if (ret != 1)
113 VG_(debugLog)(0, "scheduler",
114 "VG_(sema_down): read returned %d\n", ret);
115
116 if (ret == -VKI_EINTR)
117 goto again;
118
119 vg_assert(ret == 1); /* should get exactly 1 token */
120 vg_assert(buf[0] >= 'A' && buf[0] <= 'Z');
121 vg_assert(buf[1] == 0);
122
123 if (sema_char == 'Z') sema_char = 'A'; else sema_char++;
124
125 sema->owner_lwpid = lwpid;
126 sema->held_as_LL = as_LL;
127 }
128
129 /* put token back */
ML_(sema_up)130 void ML_(sema_up)( vg_sema_t *sema, Bool as_LL )
131 {
132 Int ret;
133 HChar buf[2];
134 vg_assert(as_LL == sema->held_as_LL);
135 buf[0] = sema_char;
136 buf[1] = 0;
137 vg_assert(sema->owner_lwpid != -1); /* must be initialised */
138 vg_assert(sema->pipe[0] != sema->pipe[1]);
139 vg_assert(sema->owner_lwpid == VG_(gettid)()); /* must have it */
140
141 sema->owner_lwpid = 0;
142
143 INNER_REQUEST(ANNOTATE_RWLOCK_RELEASED(sema, /*is_w*/1));
144 ret = VG_(write)(sema->pipe[1], buf, 1);
145
146 if (ret != 1)
147 VG_(debugLog)(0, "scheduler",
148 "VG_(sema_up):write returned %d\n", ret);
149
150 vg_assert(ret == 1);
151 }
152
153 /*--------------------------------------------------------------------*/
154 /*--- end ---*/
155 /*--------------------------------------------------------------------*/
156
157
158