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/*
test a lock wait idea
Copyright (C) Andrew Tridgell 2006
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
#include "lib/events/events.h"
#include "system/filesys.h"
#include "system/wait.h"
#include "popt.h"
#include "cmdline.h"
struct lockwait_handle {
struct fd_event *fde;
int fd[2];
pid_t child;
void *private_data;
void (*callback)(void *);
};
static void lockwait_handler(struct event_context *ev, struct fd_event *fde,
uint16_t flags, void *private_data)
{
struct lockwait_handle *h = talloc_get_type(private_data,
struct lockwait_handle);
void (*callback)(void *) = h->callback;
void *p = h->private_data;
talloc_set_destructor(h, NULL);
close(h->fd[0]);
talloc_free(h);
callback(p);
waitpid(h->child, NULL, 0);
}
static int lockwait_destructor(struct lockwait_handle *h)
{
close(h->fd[0]);
kill(h->child, SIGKILL);
waitpid(h->child, NULL, 0);
return 0;
}
static struct lockwait_handle *lockwait(struct event_context *ev,
TALLOC_CTX *mem_ctx,
int fd, off_t ofs, size_t len,
void (*callback)(void *), void *private_data)
{
struct lockwait_handle *h;
int ret;
h = talloc_zero(mem_ctx, struct lockwait_handle);
if (h == NULL) {
return NULL;
}
ret = pipe(h->fd);
if (ret != 0) {
talloc_free(h);
return NULL;
}
h->child = fork();
if (h->child == (pid_t)-1) {
close(h->fd[0]);
close(h->fd[1]);
talloc_free(h);
return NULL;
}
h->callback = callback;
h->private_data = private_data;
if (h->child == 0) {
/* in child */
struct flock lock;
close(h->fd[0]);
lock.l_type = F_WRLCK;
lock.l_whence = SEEK_SET;
lock.l_start = ofs;
lock.l_len = len;
lock.l_pid = 0;
fcntl(fd,F_SETLKW,&lock);
_exit(0);
}
close(h->fd[1]);
talloc_set_destructor(h, lockwait_destructor);
h->fde = event_add_fd(ev, h, h->fd[0], EVENT_FD_READ, lockwait_handler, h);
if (h->fde == NULL) {
talloc_free(h);
return NULL;
}
return h;
}
static void fcntl_lock_callback(void *p)
{
int *got_lock = (int *)p;
*got_lock = 1;
}
/*
get an fcntl lock - waiting if necessary
*/
static int fcntl_lock(struct event_context *ev,
int fd, int op, off_t offset, off_t count, int type)
{
struct flock lock;
int ret;
int use_lockwait = (op == F_SETLKW);
int got_lock = 0;
lock.l_type = type;
lock.l_whence = SEEK_SET;
lock.l_start = offset;
lock.l_len = count;
lock.l_pid = 0;
do {
ret = fcntl(fd,use_lockwait?F_SETLK:op,&lock);
if (ret == 0) {
return 0;
}
if (ret == -1 &&
(errno == EACCES || errno == EAGAIN || errno == EDEADLK)) {
struct lockwait_handle *h;
h = lockwait(ev, ev, fd, offset, count,
fcntl_lock_callback, &got_lock);
if (h == NULL) {
errno = ENOLCK;
return -1;
}
/* in real code we would return to the event loop */
while (!got_lock) {
event_loop_once(ev);
}
got_lock = 0;
}
} while (!got_lock);
return ret;
}
static void child(struct event_context *ev, int n)
{
int fd;
int count=0;
struct timeval tv;
fd = open("test.dat", O_CREAT|O_RDWR, 0666);
if (fd == -1) {
perror("test.dat");
exit(1);
}
tv = timeval_current();
while (timeval_elapsed(&tv) < 10) {
int ret;
ret = fcntl_lock(ev, fd, F_SETLKW, 0, 1, F_WRLCK);
if (ret != 0) {
printf("Failed to get lock in child %d!\n", n);
break;
}
fcntl_lock(ev, fd, F_SETLK, 0, 1, F_UNLCK);
count++;
}
printf("child %2d %.0f ops/sec\n", n, count/timeval_elapsed(&tv));
_exit(0);
}
static int timelimit = 10;
/*
main program
*/
int main(int argc, const char *argv[])
{
pid_t *pids;
int nprogs = 2;
int i;
struct event_context *ev;
struct poptOption popt_options[] = {
POPT_AUTOHELP
{ "timelimit", 't', POPT_ARG_INT, &timelimit, 0, "timelimit", "integer" },
{ "num-progs", 'n', POPT_ARG_INT, &nprogs, 0, "num_progs", "integer" },
POPT_TABLEEND
};
poptContext pc;
int opt;
pc = poptGetContext(argv[0], argc, argv, popt_options, POPT_CONTEXT_KEEP_FIRST);
while ((opt = poptGetNextOpt(pc)) != -1) {
switch (opt) {
default:
fprintf(stderr, "Invalid option %s: %s\n",
poptBadOption(pc, 0), poptStrerror(opt));
exit(1);
}
}
ev = event_context_init(NULL);
pids = talloc_array(ev, pid_t, nprogs);
/* create N processes fighting over the same lock */
for (i=0;i<nprogs;i++) {
pids[i] = fork();
if (pids[i] == 0) {
child(ev, i);
}
}
printf("Waiting for %d children ...\n", nprogs);
/* wait for our kids to finish playing */
for (i=0;i<nprogs;i++) {
waitpid(pids[i], NULL, 0);
}
return 0;
}
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