External checkpoint patch
Oren Laadan
orenl at cs.columbia.edu
Tue Oct 21 16:07:21 PDT 2008
> Oren,
>
> Could you take a look over Cedric's external checkpoint patch?
>
> http://git.kernel.org/?p=linux/kernel/git/daveh/linux-2.6-cr.git;a=commit;h=28ffabbc17d3641eee2a7eb66f714c266c400263
>
> It seems pretty small to me.
>
> --
I committed a couple of patches on top of ckpt-v7 that do this.
(the first one is actually a simple cleanup that is unrelated).
see:
http://git.ncl.cs.columbia.edu/?p=linux-cr-dev.git;a=shortlog;h=refs/heads/ckpt-v7
(or git://git.ncl.cs.columbia.edu/pub/git/linux-cr-dev.git ckpt-v7)
* "Minor simplification of cr_ctx_alloc(), cr_ctx_free()"
* "External checkpoint of a task other than ourself"
To checkpoint another task, you need to freeze that other task, or to
SIGSTOP it (if using a kernel without freezer cgroup).
Restart remains the same except the the original PID is not preserved
(because we haven't solved yet the fork-with-specific-pid issue).
In reality, you would create a new names space, and have the task running
in there call 'sys_restart()'.
Below are test1.c, ckpt.c (to checkpoint), and rstr.c (to restart), as
well as the two patches.
I tested it this way:
$ ./test.1 &
[1] 3493
$ kill -STOP 3493
$ ./ckpt 3493 > ckpt.image
$ mv /tmp/cr-test.out /tmp/cr-test.out.orig
$ cp /tmp/cr-test.out.orig /tmp/cr-test.out
$ kill -CONT 3493
$ ./rstr < ckpt.image
now compare the output of the two output files
Oren.
------------------------------------------------------------------------
#define _GNU_SOURCE /* or _BSD_SOURCE or _SVID_SOURCE */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <math.h>
#include <asm/unistd.h>
#define OUTFILE "/tmp/cr-test.out"
int main(int argc, char *argv[])
{
FILE *file;
float a;
int i;
close(0);
close(1);
close(2);
unlink(OUTFILE);
file = fopen(OUTFILE, "w+");
if (!file) {
perror("open");
exit(1);
}
if (dup2(0,2) < 0) {
perror("dup2");
exit(1);
}
a = sqrt(2.53 * (getpid() / 1.21));
fprintf(file, "hello, world (%.2f)!\n", a);
fflush(file);
for (i = 0; i < 1000; i++) {
sleep(1);
/* make the fpu work -> a = a + i/10 */
a = sqrt(a*a + 2*a*(i/10.0) + i*i/100.0);
fprintf(file, "count %d (%.2f)!\n", i, a);
fflush(file);
}
fprintf(file, "world, hello (%.2f) !\n", a);
fflush(file);
return 0;
}
------------------------------------------------------------------------
#define _GNU_SOURCE /* or _BSD_SOURCE or _SVID_SOURCE */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <asm/unistd.h>
#include <sys/syscall.h>
int main(int argc, char *argv[])
{
pid_t pid;
int ret;
if (argc != 2) {
printf("usage: ckpt PID\n");
exit(1);
}
pid = atoi(argv[1]);
if (pid <= 0) {
printf("invalid pid\n");
exit(1);
}
ret = syscall(__NR_checkpoint, pid, STDOUT_FILENO, 0);
if (ret < 0)
perror("checkpoint");
else
printf("checkpoint id %d\n", ret);
return (ret > 0 ? 0 : 1);
}
------------------------------------------------------------------------
#define _GNU_SOURCE /* or _BSD_SOURCE or _SVID_SOURCE */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <asm/unistd.h>
#include <sys/syscall.h>
int main(int argc, char *argv[])
{
pid_t pid = getpid();
int ret;
ret = syscall(__NR_restart, pid, STDIN_FILENO, 0);
if (ret < 0)
perror("restart");
printf("should not reach here !\n");
return 0;
}
------------------------------------------------------------------------
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