Messages in this thread | | | From | (Eric W. Biederman) | Date | Wed, 10 Mar 2021 16:13:06 -0600 | Subject | Re: [PATCH] exit: trigger panic when init process is set to SIGNAL_GROUP_EXIT |
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Oleg Nesterov <oleg@redhat.com> writes:
> On 03/10, Eric W. Biederman wrote: >> >> /* If global init has exited, >> * panic immediately to get a useable coredump. >> */ >> if (unlikely(is_global_init(tsk) && >> (thread_group_empty(tsk) || >> (tsk->signal->flags & SIGNAL_GROUP_EXIT)))) { >> panic("Attempted to kill init! exitcode=0x%08x\n", >> tsk->signal->group_exit_code ?: (int)code); >> } >> >> The thread_group_empty test is needed to handle single threaded >> inits. > > But we can't rely on thread_group_empty(). Just suppose that the main > thread exit first, then the 2nd (last) thread exits too.
It took me a minute. I think you are pointing out that there is a case where we do not set SIGNAL_GROUP_EXIT and that init actually exits.
The case where all of the threads do pthread_exit() aka do_exit().
I think that implies that to have a comprehensive test would need to do:
group_dead = atomic_dec_and_test(&tsk->signal->live);
/* If global init has exited, * panic immediately to get a useable coredump. */ if (unlikely(is_global_init(tsk) && (group_dead || thread_group_empty(tsk) || (tsk->signal->flags & SIGNAL_GROUP_EXIT)))) { panic("Attempted to kill init! exitcode=0x%08x\n", tsk->signal->group_exit_code ?: (int)code); }
Leaving the test where it is. Yes. I think that should work.
Eric
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