From: Paul H. Hargrove (PHHargrove_at_lbl_dot_gov)
Date: Fri Dec 28 2007 - 16:29:44 PST
王磊 wrote:
> Dear Sir ,
>
> Yesterday , I wrote to you for help ,today I have another question .
>
> I guess if I can directly call " cr_restart" in system() function ? In
> my program there is some problems .
>
> The form of my program is as follows :
>
> ................
> checkpoint_func() ; //place1 , successfully ,and I
> have a checkpoint file named as " filename"
> ................
> ...............
> system( " cr_restart filename") ;//I want to
> imitate the command-line form to let it go to place1
>
> .............
> but , the error told me that " open (filename, O_RDONLY): No Such file
> or directory "
>
> So , I write another program to seperately use system() function ,it
> meets my request.
>
> I can not understand , would you help me ?
>
> Thanks !
>
> Daniel.
Daniel,
Sorry for the slow response - this is a vacation week for most of us.
Your use of system() is the correct approach - there is NOT yet any
cr_request_restart() type of function in our library because the
interface is still changing. For now, use of system() is the only
recommended way.
As to why you get "No such file or directory" I can only guess that
the file is not where you expect it, or that your program's cwd is not
the same as when the file was created. You might want to check if
system("ls -l filename") works or not when called exactly where you have
system("cr_restart filename") now.
Aside from the "No such file or directory" error, you are probably not
going to be able to do what you are trying (a program requesting its own
restart) because BLCR can't restart a process when its PID is already in
use, and doesn't currently have a mechanism to say "replace *this*
process with the restarted one". If the program is to restart itself,
it will need to fork a child to request the restart, and will itself
need to exit before the restart can succeed. Something like the
following (compiled but not tested for an actual restart) is probably
what you want. This function will return only if there is a failure
prior to the fork().
-Paul
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
int restart_self(const char *filename) {
int pid;
int fds[2];
int rc;
/* Create pipe to allow child to wait for parent's death */
rc = pipe(fds);
if (rc < 0) {
perror("pipe() call failed");
return -1;
}
/* Fork a child */
pid = fork();
if (pid < 0) {
perror("fork() call failed");
return -1;
} else if (pid > 0) {
/* In parent - just exit */
exit(0);
}
/* In child - wait for parent's death (EOF on pipe) */
close(fds[1]);
do {
char dummy;
rc = read(fds[0], &dummy, 1);
} while ((rc < 0) && (errno == EINTR));
if (rc != 0) {
perror("read() call failed in an unexpected way");
exit(1);
}
/* Restart */
rc = execlp("cr_restart", "cr_restart", filename, NULL);
perror("exec() returned!");
exit(1);
}
--
Paul H. Hargrove PHHargrove_at_lbl_dot_gov
Future Technologies Group
HPC Research Department Tel: +1-510-495-2352
Lawrence Berkeley National Laboratory Fax: +1-510-486-6900