On 12/06, Andrew Morton wrote:
> On Sun, 4 Dec 2011 21:24:50 +0100
> Daniel Lezcano <daniel.lezcano@xxxxxxx> wrote:
>
> > This patch propose to store the reboot value in the 16 upper bits of the
> > exit code from the processes belonging to a pid namespace which has
> > rebooted. When the reboot syscall is called and we are not in the initial
> > pid namespace, we kill the pid namespace.
> >
> > By this way the parent process of the child pid namespace to know if
> > it rebooted or not and take the right decision.
>
> hm, modifying the exit code in this manner is a strange interface. I
> didn't see that coming. Perhaps some additional justification for this
> idea should be added to the changelog, along with discussion of
> alternative schemes. I don't immediately see any problems with it,
> but, odd... I wonder what potential it has to upset existing
> userspace.
Alternatively, we could do something like
switch (reboot) {
case LINUX_REBOOT_CMD_RESTART:
exit_code = SIGHUP;
break;
case LINUX_REBOOT_CMD_HALT:
exit_code = SIGINT;
break;
...
}
this way the parent can check WIFSIGNALED/WTERMSIG instead of upper bits.
This was the initial suggestion, and personally I like this more.
But I do not think this can upset existing userspace. __WEXITSTATUS()
reports the lower bits only, it can't see the extra info we add.
> Also, this affects the data delivered by taskstats, I believe. Please
> check this, test it, document it in the changelog and update
> getdelays.c appropriately.
No, taskstats report ->exit_code. This doesn't look right btw. But
in any case I do not think this can break something.
> Also, glibc might be affected. For symmetry we might want to add a
> WIFREBOOT() or something.
We already use these upper bits to report the ptrace events, in the
same manner. I do not think this has something to do with libc.
Although it could probably have another macro to read this info.
> And we now expect waitid() to fill in extra
> bits in siginfo_t.si_status, which assumes that glibc (and other
> libc's!) aren't using a u8 in there somewhere. etcetera. This all
> should be tested, and reviewed by Uli (please).
Again, ptrace already puts the extra info this way when the tracee
stops.
Oleg.
_______________________________________________
Containers mailing list
Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/containers
