coregrind/m_scheduler/sema.c

   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, see <http://www.gnu.org/licenses/>.
  25
  26    The GNU General Public License is contained in the file COPYING.
  27 */
  28
  29 #include "pub_core_basics.h"
  30 #include "pub_core_debuglog.h"
  31 #include "pub_core_vki.h"
  32 #include "pub_core_libcassert.h"
  33 #include "pub_core_libcfile.h"
  34 #include "pub_core_libcproc.h"      // For VG_(gettid)()
  35 #include "pub_core_inner.h"
  36 #if defined(ENABLE_INNER_CLIENT_REQUEST)
  37 #include "helgrind/helgrind.h"
  38 #endif
  39 #include "priv_sema.h"
  40
  41 /*
  42    Slower (than the removed futex-based sema scheme) but more portable
  43    pipe-based token passing scheme.
  44  */
  45
  46 /* Cycle the char passed through the pipe through 'A' .. 'Z' to make
  47    it easier to make sense of strace/truss output - makes it possible
  48    to see more clearly the change of ownership of the lock.  Need to
  49    be careful to reinitialise it at fork() time. */
  50 static HChar sema_char = '!'; /* will cause assertion failures if used
  51                                  before sema_init */
  52
  53 void ML_(sema_init)(vg_sema_t *sema)
  54 {
  55    HChar buf[2];
  56    Int res, r;
  57    r = VG_(pipe)(sema->pipe);
  58    vg_assert(r == 0);
  59
  60    vg_assert(sema->pipe[0] != sema->pipe[1]);
  61
  62    sema->pipe[0] = VG_(safe_fd)(sema->pipe[0]);
  63    sema->pipe[1] = VG_(safe_fd)(sema->pipe[1]);
  64
  65    if (0)
  66       VG_(debugLog)(0,"zz","sema_init: %d %d\n", sema->pipe[0],
  67                                                  sema->pipe[1]);
  68    vg_assert(sema->pipe[0] != sema->pipe[1]);
  69
  70    sema->owner_lwpid = -1;
  71
  72    /* create initial token */
  73    sema_char = 'A';
  74    buf[0] = sema_char;
  75    buf[1] = 0;
  76    sema_char++;
  77    INNER_REQUEST(ANNOTATE_RWLOCK_CREATE(sema));
  78    INNER_REQUEST(ANNOTATE_BENIGN_RACE_SIZED(&sema->owner_lwpid,
  79                                             sizeof(sema->owner_lwpid), ""));
  80    res = VG_(write)(sema->pipe[1], buf, 1);
  81    vg_assert(res == 1);
  82 }
  83
  84 void ML_(sema_deinit)(vg_sema_t *sema)
  85 {
  86    vg_assert(sema->owner_lwpid != -1); /* must be initialised */
  87    vg_assert(sema->pipe[0] != sema->pipe[1]);
  88    INNER_REQUEST(ANNOTATE_RWLOCK_DESTROY(sema));
  89    VG_(close)(sema->pipe[0]);
  90    VG_(close)(sema->pipe[1]);
  91    sema->pipe[0] = sema->pipe[1] = -1;
  92    sema->owner_lwpid = -1;
  93 }
  94
  95 /* get a token */
  96 void ML_(sema_down)( vg_sema_t *sema, Bool as_LL )
  97 {
  98    HChar buf[2];
  99    Int ret;
 100    Int lwpid = VG_(gettid)();
 101
 102    vg_assert(sema->owner_lwpid != lwpid); /* can't have it already */
 103    vg_assert(sema->pipe[0] != sema->pipe[1]);
 104
 105   again:
 106    buf[0] = buf[1] = 0;
 107    ret = VG_(read)(sema->pipe[0], buf, 1);
 108    INNER_REQUEST(ANNOTATE_RWLOCK_ACQUIRED(sema, /*is_w*/1));
 109
 110    if (ret != 1)
 111       VG_(debugLog)(0, "scheduler",
 112                        "VG_(sema_down): read returned %d\n", ret);
 113
 114    if (ret == -VKI_EINTR)
 115       goto again;
 116
 117    vg_assert(ret == 1);         /* should get exactly 1 token */
 118    vg_assert(buf[0] >= 'A' && buf[0] <= 'Z');
 119    vg_assert(buf[1] == 0);
 120
 121    if (sema_char == 'Z') sema_char = 'A'; else sema_char++;
 122
 123    sema->owner_lwpid = lwpid;
 124    sema->held_as_LL = as_LL;
 125 }
 126
 127 /* put token back */
 128 void ML_(sema_up)( vg_sema_t *sema, Bool as_LL )
 129 {
 130    Int ret;
 131    HChar buf[2];
 132    vg_assert(as_LL == sema->held_as_LL);
 133    buf[0] = sema_char;
 134    buf[1] = 0;
 135    vg_assert(sema->owner_lwpid != -1); /* must be initialised */
 136    vg_assert(sema->pipe[0] != sema->pipe[1]);
 137    vg_assert(sema->owner_lwpid == VG_(gettid)()); /* must have it */
 138
 139    sema->owner_lwpid = 0;
 140
 141    INNER_REQUEST(ANNOTATE_RWLOCK_RELEASED(sema, /*is_w*/1));
 142    ret = VG_(write)(sema->pipe[1], buf, 1);
 143
 144    if (ret != 1)
 145       VG_(debugLog)(0, "scheduler",
 146                        "VG_(sema_up):write returned %d\n", ret);
 147
 148    vg_assert(ret == 1);
 149 }
 150
 151 /*--------------------------------------------------------------------*/
 152 /*--- end                                                          ---*/
 153 /*--------------------------------------------------------------------*/
 154
 155