Reproducible panic - Going nowhere without my init!

[Graham Menhennitt]

Let me preface this by saying that I know nothing about this particular 
bit of code, but...

As a general rule, I would question the use of gettimeofday() while 
panicing. At that stage, everything could have already gone down the 
plug hole.

That said, it already calls sleep(), so maybe that uses the same 
gettimeofday() call internally. In which case, please ignore this comment.

Graham


On 7/10/2016 9:32 AM, Andy Farkas wrote:
> With your latest patch applied, I ran through my procedure more
> than a dozen times and no panics!
>
> Any explanation why sleep(STALL_TIMEOUT) as apposed to a
> bunch of sleep(1)'s tickles the panic?
>
> Also, it is definitely not sleeping for 30 seconds. I guess some
> event interrupts the sleep loop?
>
> Thanks heaps for your time and effort,
>
> -andyf
>
> %%%
> Please try the following patch.
>
> diff --git a/sbin/init/init.c b/sbin/init/init.c
> index bda86b5..25ac2bd 100644
> --- a/sbin/init/init.c
> +++ b/sbin/init/init.c
> @@ -870,6 +870,7 @@ single_user(void)
>    sigset_t mask;
>    const char *shell;
>    char *argv[2];
> + struct timeval tv, tn;
>   #ifdef SECURE
>    struct ttyent *typ;
>    struct passwd *pp;
> @@ -884,8 +885,13 @@ single_user(void)
>    if (Reboot) {
>    /* Instead of going single user, let's reboot the machine */
>    sync();
> - reboot(howto);
> - _exit(0);
> + if (reboot(howto) == -1) {
> + emergency("reboot(%#x) failed, %s", howto,
> +    strerror(errno));
> + _exit(1); /* panic and reboot */
> + }
> + warning("reboot(%#x) returned", howto);
> + _exit(0); /* panic as well */
>    }
>
>    shell = get_shell();
> @@ -1002,7 +1008,14 @@ single_user(void)
>    *  reboot(8) killed shell?
>    */
>    warning("single user shell terminated.");
> - sleep(STALL_TIMEOUT);
> + gettimeofday(&tv, NULL);
> + tn = tv;
> + tv.tv_sec += STALL_TIMEOUT;
> + while (tv.tv_sec > tn.tv_sec || (tv.tv_sec ==
> +    tn.tv_sec && tv.tv_usec > tn.tv_usec)) {
> + sleep(1);
> + gettimeofday(&tn, NULL);
> + }
>    _exit(0);
>    } else {
>    warning("single user shell terminated, restarting");
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