1#!/bin/sh 2 3# 4# Copyright (c) 2014 EMC Corp. 5# All rights reserved. 6# 7# Redistribution and use in source and binary forms, with or without 8# modification, are permitted provided that the following conditions 9# are met: 10# 1. Redistributions of source code must retain the above copyright 11# notice, this list of conditions and the following disclaimer. 12# 2. Redistributions in binary form must reproduce the above copyright 13# notice, this list of conditions and the following disclaimer in the 14# documentation and/or other materials provided with the distribution. 15# 16# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26# SUCH DAMAGE. 27# 28 29# fcntl(2) locking scenario. No problems seen. 30 31. ../default.cfg 32 33here=`pwd` 34cd /tmp 35sed '1,/^EOF/d' < $here/$0 > fcntl.c 36mycc -o fcntl -Wall -Wextra -O0 -g fcntl.c || exit 1 37rm -f fcntl.c 38 39mkdir -p $RUNDIR 40cd $RUNDIR 41/tmp/fcntl 42status=$? 43 44rm -f /tmp/fcntl 45exit $status 46EOF 47#include <sys/types.h> 48#include <err.h> 49#include <errno.h> 50#include <fcntl.h> 51#include <signal.h> 52#include <stdio.h> 53#include <stdlib.h> 54#include <string.h> 55#include <sys/wait.h> 56#include <unistd.h> 57 58#define PARALLEL 16 59#define N 4096 60 61static volatile sig_atomic_t completed; 62const char name[] = "work"; 63int fd; 64 65static void 66ahandler(int s __unused) 67{ 68 unlink(name); 69 _exit(1); 70} 71 72static void 73handler(int s __unused) 74{ 75 completed++; 76} 77 78void 79add(int n, int increment) 80{ 81 struct flock fl; 82 off_t pos; 83 long val, oval __unused; 84 int r; 85 86 pos = n * sizeof(val); 87 memset(&fl, 0, sizeof(fl)); 88 fl.l_start = pos; 89 fl.l_len = sizeof(val); 90 fl.l_type = F_WRLCK; 91 fl.l_whence = SEEK_SET; 92 93 while (fcntl(fd, F_SETLK, &fl) < 0) { 94 if (errno != EAGAIN) 95 err(1, "F_SETLK (child)"); 96 usleep(100); 97 } 98 99 if (lseek(fd, pos, SEEK_SET) == -1) 100 err(1, "lseek"); 101 oval = 999999; 102 while ((r = read(fd, &val, sizeof(val)) != sizeof(val))) { 103 if (r == -1 && errno != EAGAIN) 104 err(1, "read"); 105 if (lseek(fd, pos, SEEK_SET) == -1) 106 err(1, "lseek"); 107 } 108 oval = val; 109 val = val + increment; 110#if defined(DEBUG) 111 fprintf(stderr, "add(%d, %d) @ pos %ld: %ld = %ld + %d\n", 112 n, increment, (long)pos, val, oval, increment); 113#endif 114 if (lseek(fd, pos, SEEK_SET) == -1) 115 err(1, "lseek"); 116 while ((r = write(fd, &val, sizeof(val)) != sizeof(val))) { 117 if (r == -1 && errno != EAGAIN) 118 err(1, "write"); 119 if (lseek(fd, pos, SEEK_SET) == -1) 120 err(1, "lseek"); 121 } 122 123 fl.l_type = F_UNLCK; 124 if (fcntl(fd, F_SETLK, &fl) < 0) 125 err(1, "F_UNLCK"); 126 127} 128 129void 130up(void) 131{ 132 int flags, i; 133 134 /* Need to re-open after a fork() */ 135 close(fd); 136 if ((fd = open(name, O_RDWR)) == -1) 137 err(1, "open(%s)", name); 138 if ((flags = fcntl(fd, F_GETFL)) == -1) 139 err(1, "fcntl(%d, T_GETFL)", fd); 140 flags |= O_NONBLOCK; 141 if ((flags = fcntl(fd, F_SETFL, flags)) == -1) 142 err(1, "fcntl(%d, T_SETFL, %d)", fd, flags); 143 144 for (i = 0; i < N; i++) 145 add(i, 1); 146 147 kill(getppid(), SIGHUP); 148 while (access("work", R_OK) == 0) 149 usleep(100); 150 151 _exit(0); 152} 153 154void 155down(void) 156{ 157 int flags, i; 158 159 close(fd); 160 if ((fd = open(name, O_RDWR)) == -1) 161 err(1, "open(%s)", name); 162 if ((flags = fcntl(fd, F_GETFL)) == -1) 163 err(1, "fcntl(%d, T_GETFL)", fd); 164 flags |= O_NONBLOCK; 165 if ((flags = fcntl(fd, F_SETFL, flags)) == -1) 166 err(1, "fcntl(%d, T_SETFL, %d)", fd, flags); 167 168 for (i = 0; i < N; i++) 169 add(i, -1); 170 171 kill(getppid(), SIGHUP); 172 while (access("work", R_OK) == 0) 173 usleep(100); 174 175 _exit(0); 176} 177 178int 179main(void) 180{ 181 int flags, i; 182 long val, sum; 183 off_t len; 184 185 signal(SIGHUP, handler); 186 signal(SIGALRM, ahandler); 187 alarm(300); 188 if ((fd = open(name, O_RDWR | O_CREAT | O_TRUNC, 0640)) == -1) 189 err(1, "open(%s)", name); 190 len = N * sizeof(val); 191 if (ftruncate(fd, len) == -1) 192 err(1, "ftruncate"); 193 194 if ((flags = fcntl(fd, F_GETFL)) == -1) 195 err(1, "fcntl(%d, T_GETFL)", fd); 196 flags |= O_NONBLOCK; 197 if ((flags = fcntl(fd, F_SETFL, flags)) == -1) 198 err(1, "fcntl(%d, T_SETFL, %d)", fd, flags); 199 200 for (i = 0; i < PARALLEL; i++) { 201 if (fork() == 0) 202 up(); 203 } 204 for (i = 0; i < PARALLEL; i++) { 205 if (fork() == 0) 206 down(); 207 } 208 209 while (completed != PARALLEL * 2) 210 usleep(200); 211 212 if (lseek(fd, 0, SEEK_SET) == -1) 213 err(1, "lseek"); 214 sum = 0; 215 for (i = 0; i < N; i++) { 216 if (read(fd, &val, sizeof(val)) != sizeof(val)) 217 err(1, "Final read"); 218 if (val != 0) 219 fprintf(stderr, "index %d: %ld\n", i, val); 220 sum += val; 221 } 222 if (sum != 0) 223 fprintf(stderr, "FAIL\n"); 224 unlink(name); 225 226 for (i = 0; i < PARALLEL; i++) { 227 wait(NULL); 228 wait(NULL); 229 } 230 231 close(fd); 232 233 return (sum != 0); 234} 235