Hi Serge,
On 30/11/09 14:22 -0600, Serge E. Hallyn wrote:
> We currently checkpoint and restart unix98 ptys in the kernel.
> So what do we want to do about the userspace part? In particular,
> if I run the following test program and checkpoint it, it
> has `tty` open. What do we want to do about that?
>
> Just having user-cr/restart.c take an option to mount a new
> instance of devpts isn't enough - we don't get hooked up to
> restart.c's stdin/out obviously, and restart succeeds but the
> restarted program exists with -EIO. At the same time, just
> doing a cradvise type of thing to plug fds 0,1,2 suffice for
> this testcase, but not for something more complicated which
> also has other unix98 ptys open.
In Kerrighed we are implementing something à-la-cradvise: we allow the
caller of sys_restart() to give replacement fds for arbitrary files. To achieve
this, each checkpointed file descriptor (struct file) has a unique key, and
sys_restart() takes a substitution table in parameter, where an entry is a
pair (key, fd).
In Kerrighed sys_checkpoint() exports a human-readable table of checkpointed
file descriptors, with types, fd in each checkpointed task, etc.
With Oren's patchset, I presume that some userspace tool could extract such a
table from the checkpoint.
Hope this makes the discussion progress...
Louis
>
> Do we require that it be run in screen? Then what about the
> screen session's terminals themselves?
>
> Anyway, I have this feeling that other have already thought
> through this, so here is the simple program for discussion:
>
> #include <stdio.h>
> #include <curses.h>
> #include <string.h>
>
> int main(int argc, char *argv[])
> {
> #define MAXLEN 20
> char input[MAXLEN+1];
> int i = 0;
>
> initscr();
> cbreak();
> //noecho();
> nonl();
> intrflush(stdscr, FALSE);
> keypad(stdscr, TRUE);
>
> addstr("Enter some text: ");
> memset(input, 0, MAXLEN+1);
> while (1) {
> input[i] = getch();
> if (input[i] == KEY_ENTER || input[i]=='\r')
> break;
> i++;
> if (i == MAXLEN)
> break;
> }
> endwin();
> printf("I read the text: %s\n", input);
> return 0;
> }
>
> -serge
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--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes
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