273 lines
6.6 KiB
C
273 lines
6.6 KiB
C
/*
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* Copyright (c) 2014
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* The President and Fellows of Harvard College.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* multiexec - stuff N procs into exec at once
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* usage: multiexec [-j N] [prog [arg...]]
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*
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* This can be used both to see what happens when you have a lot of
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* execs at once (its original purpose) by running ordinary programs
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* like pwd (the default) and also just as a workload generator /
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* convenient way to start lots of copies of things at once.
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*
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* Note that this uses execv directly (not execvp) so it doesn't
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* search $PATH for the program you want to run, and therefore it
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* needs full paths. One could make it use execvp; it doesn't because
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* that would complicate its coordinated startup logic, and also get
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* in the way of using it to debug execv.
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*
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* Some things to try:
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* multiexec /bin/true
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* multiexec /bin/cat foo (for some file foo)
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* multiexec /testbin/add 3 8
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* Some more aggressive things to try:
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* multiexec /testbin/factorial 15
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* multiexec /testbin/bigexec
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* multiexec /testbin/sort (once you have a VM system)
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* Some mean things:
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* multiexec /testbin/forktest
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* multiexec /testbin/bloat (once you have sbrk)
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* multiexec /bin/sh (this makes a huge mess unless you have job control)
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <err.h>
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////////////////////////////////////////////////////////////
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// semaphores
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/*
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* We open the semaphore separately in each process to avoid
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* filehandle-level locking problems. If you can't be "reading" and
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* "writing" the semaphore concurrently because of the open file
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* object lock, then using the same file handle for P and V will
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* deadlock. Also, if this same lock is used to protect the reference
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* count on the open file logic, fork will block if another process is
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* using the same file handle for P, and then we're deadlocked too.
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*
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* Ideally the open file / filetable code wouldn't have this problem,
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* as it makes e.g. console output from background jobs behave
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* strangely, but it's a common issue in practice and it's better for
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* tests to be immune to it.
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*/
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struct usem {
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char name[32];
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int fd;
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};
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static
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void
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semcreate(const char *tag, struct usem *sem)
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{
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int fd;
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snprintf(sem->name, sizeof(sem->name), "sem:multiexec.%s.%d",
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tag, (int)getpid());
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fd = open(sem->name, O_WRONLY|O_CREAT|O_TRUNC, 0664);
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if (fd < 0) {
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err(1, "%s: create", sem->name);
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}
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close(fd);
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}
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static
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void
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semopen(struct usem *sem)
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{
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sem->fd = open(sem->name, O_RDWR, 0664);
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if (sem->fd < 0) {
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err(1, "%s: open", sem->name);
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}
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}
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static
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void
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semclose(struct usem *sem)
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{
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close(sem->fd);
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}
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static
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void
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semdestroy(struct usem *sem)
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{
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remove(sem->name);
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}
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static
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void
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semP(struct usem *sem, size_t num)
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{
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char c[num];
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if (read(sem->fd, c, num) < 0) {
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err(1, "%s: read", sem->name);
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}
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(void)c;
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}
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static
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void
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semV(struct usem *sem, size_t num)
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{
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char c[num];
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/* semfs does not use these values, but be conservative */
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memset(c, 0, num);
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if (write(sem->fd, c, num) < 0) {
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err(1, "%s: write", sem->name);
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}
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}
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////////////////////////////////////////////////////////////
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// test
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#define SUBARGC_MAX 64
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static char *subargv[SUBARGC_MAX];
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static int subargc = 0;
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static
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void
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spawn(int njobs)
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{
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struct usem s1, s2;
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pid_t pids[njobs];
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int failed, status;
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int i;
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semcreate("1", &s1);
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semcreate("2", &s2);
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tprintf("Forking %d child processes...\n", njobs);
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for (i=0; i<njobs; i++) {
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pids[i] = fork();
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if (pids[i] == -1) {
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/* continue with the procs we have; cannot kill them */
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warn("fork");
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warnx("*** Only started %u processes ***", i);
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njobs = i;
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break;
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}
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if (pids[i] == 0) {
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/* child */
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semopen(&s1);
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semopen(&s2);
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semV(&s1, 1);
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semP(&s2, 1);
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semclose(&s1);
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semclose(&s2);
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execv(subargv[0], subargv);
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warn("execv: %s", subargv[0]);
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_exit(1);
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}
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}
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semopen(&s1);
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semopen(&s2);
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tprintf("Waiting for fork...\n");
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semP(&s1, njobs);
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tprintf("Starting the execs...\n");
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semV(&s2, njobs);
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failed = 0;
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for (i=0; i<njobs; i++) {
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if (waitpid(pids[i], &status, 0) < 0) {
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warn("waitpid");
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failed++;
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}
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else if (WIFSIGNALED(status)) {
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warnx("pid %d (child %d): Signal %d",
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(int)pids[i], i, WTERMSIG(status));
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failed++;
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}
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else if (WIFEXITED(status) && WEXITSTATUS(status) != 0) {
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warnx("pid %d (child %d): Exit %d",
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(int)pids[i], i, WEXITSTATUS(status));
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failed++;
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}
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}
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if (failed > 0) {
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warnx("%d children failed", failed);
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}
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else {
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tprintf("Succeeded\n");
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}
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semclose(&s1);
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semclose(&s2);
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semdestroy(&s1);
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semdestroy(&s2);
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}
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int
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main(int argc, char *argv[])
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{
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static char default_prog[] = "/bin/pwd";
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int njobs = 12;
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int i;
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for (i=1; i<argc; i++) {
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if (!strcmp(argv[i], "-j")) {
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i++;
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if (argv[i] == NULL) {
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errx(1, "Option -j requires an argument");
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}
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njobs = atoi(argv[i]);
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}
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#if 0 /* XXX we apparently don't have strncmp? */
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else if (!strncmp(argv[i], "-j", 2)) {
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njobs = atoi(argv[i] + 2);
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}
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#endif
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else {
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subargv[subargc++] = argv[i];
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if (subargc >= SUBARGC_MAX) {
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errx(1, "Too many arguments");
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}
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}
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}
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if (subargc == 0) {
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subargv[subargc++] = default_prog;
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}
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subargv[subargc] = NULL;
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spawn(njobs);
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return 0;
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}
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