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#!/bin/sh
#
# Copyright (c) 2016 EMC Corp.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# From r238952's commit log:
# The first change closes a race where an open() that will block with O_SHLOCK
# or O_EXLOCK can increase the write count while it waits. If the process
# holding the current lock on the file then tries to call exec() on the file
# it has locked, it can fail with ETXTBUSY even though the advisory lock is
# preventing other threads from successfully completing a writable open().
#
# The second change closes a race where a read-only open() with O_SHLOCK or
# O_EXLOCK may return successfully while the write count is non-zero due to
# another descriptor that had the advisory lock and was blocking the open()
# still being in the process of closing. If the process that completed the
# open() then attempts to call exec() on the file it locked, it can fail with
# ETXTBUSY even though the other process that held a write lock has closed
# the file and released the lock.
# https://people.freebsd.org/~pho/stress/log/kostik859.txt
# https://people.freebsd.org/~pho/stress/log/kostik860.txt
# Fixed by r294204.
. ../default.cfg
[ `id -u ` -ne 0 ] && echo "Must be root!" && exit 1
dir=/tmp
odir=`pwd`
cd $dir
sed '1,/^EOF/d' < $odir/$0 > $dir/advlock.c
mycc -o advlock -Wall -Wextra -O0 -g advlock.c || exit 1
rm -f advlock.c
mount | grep "on $mntpoint " | grep -q /dev/md && umount -f $mntpoint
mdconfig -l | grep -q md$mdstart && mdconfig -d -u $mdstart
mdconfig -a -t swap -s 512m -u $mdstart || exit 1
bsdlabel -w md$mdstart auto
newfs $newfs_flags md${mdstart}$part > /dev/null
mount /dev/md${mdstart}$part $mntpoint
cp /usr/bin/true $mntpoint
cd $mntpoint
/tmp/advlock
r=$?
cd $odir
while mount | grep "on $mntpoint " | grep -q /dev/md; do
umount $mntpoint || sleep 1
done
mdconfig -d -u $mdstart
rm -f /tmp/advlock
exit $r
EOF
#include <sys/param.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <machine/atomic.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
volatile u_int *share;
char *cmdline[] = { "./true", NULL };
const char *tp;
#define SYNC 0
#define PARALLEL 2
#define RUNTIME (1 * 60)
void
handler(int i __unused) {
fprintf(stderr, "ALARM from %s.\n", tp);
_exit(1);
}
void
slock(void)
{
int fd;
setproctitle("%s", __func__);
atomic_add_int(&share[SYNC], 1);
while (share[SYNC] != PARALLEL)
;
tp = __func__;
alarm(2);
if ((fd = open(cmdline[0], O_RDONLY | O_SHLOCK)) == -1)
err(1, "open(%s). %d", cmdline[0], __LINE__);
usleep(500);
close(fd);
_exit(0);
}
void
elock(void)
{
int fd;
setproctitle("%s", __func__);
atomic_add_int(&share[SYNC], 1);
while (share[SYNC] != PARALLEL)
;
tp = __func__;
alarm(2);
if ((fd = open(cmdline[0], O_WRONLY | O_EXLOCK)) == -1) {
if (errno != ETXTBSY)
err(1, "open(%s). %d", cmdline[0], __LINE__);
} else {
usleep(500);
close(fd);
}
_exit(0);
}
void
stest(void)
{
int fd;
setproctitle("%s", __func__);
atomic_add_int(&share[SYNC], 1);
while (share[SYNC] != PARALLEL)
;
tp = __func__;
alarm(2);
if ((fd = open(cmdline[0], O_RDONLY | O_SHLOCK)) == -1)
err(1, "open(%s). %d", cmdline[0], __LINE__);
if (execve(cmdline[0], cmdline, NULL) == -1)
err(1, "execve(%s) @ %d", cmdline[0], __LINE__);
_exit(0);
}
void
etest(void)
{
int fd;
setproctitle("%s", __func__);
atomic_add_int(&share[SYNC], 1);
while (share[SYNC] != PARALLEL)
;
tp = __func__;
alarm(2);
if ((fd = open(cmdline[0], O_RDONLY | O_EXLOCK)) == -1)
err(1, "open(%s). %d", cmdline[0], __LINE__);
if (execve(cmdline[0], cmdline, NULL) == -1)
err(1, "execve(%s) @ %d", cmdline[0], __LINE__);
_exit(0);
}
int
main(void)
{
size_t len;
time_t start;
int i, n, r, s;
len = PAGE_SIZE;
if ((share = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_ANON | MAP_SHARED,
-1, 0)) == MAP_FAILED)
err(1, "mmap");
signal(SIGALRM, handler);
n = r = 0;
start = time(NULL);
while ((time(NULL) - start) < RUNTIME) {
n++;
share[SYNC] = 0;
if (fork() == 0)
slock();
if (fork() == 0)
stest();
for (i = 0; i < PARALLEL; i++) {
wait(&s);
r += s == 0 ? 0 : 1;
}
if (r != 0)
break;
share[SYNC] = 0;
if (fork() == 0)
elock();
if (fork() == 0)
etest();
for (i = 0; i < PARALLEL; i++) {
wait(&s);
r += s == 0 ? 0 : 1;
}
if (r != 0)
break;
}
if (r != 0)
fprintf(stderr, "FAIL @ %d\n", n);
return (r);
}
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