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) 2000-2012 Julian Seward 11 jseward (at) 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_tool_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 Char sema_char = '!'; /* will cause assertion failures if used 53 before sema_init */ 54 55 void ML_(sema_init)(vg_sema_t *sema) 56 { 57 Char 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 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 */ 98 void ML_(sema_down)( vg_sema_t *sema, Bool as_LL ) 99 { 100 Char 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 */ 130 void ML_(sema_up)( vg_sema_t *sema, Bool as_LL ) 131 { 132 Int ret; 133 Char 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
