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    SubjectRe: [PATCH v2] kernel/exit: do panic earlier to get coredump if global init task exit
    On 12/17, chenqiwu wrote:
    >
    > @@ -728,6 +724,15 @@ void __noreturn do_exit(long code)
    > panic("Attempted to kill the idle task!");
    >
    > /*
    > + * If all threads of global init have exited, do panic imeddiately
    > + * to get the coredump to find any clue for init task in userspace.
    > + */
    > + if (unlikely(is_global_init(tsk) &&
    > + (atomic_read(&tsk->signal->live) == 1)))

    Well, I guess this will work in practice, but in theory this is racy.

    Suppose that signal->live == 2 and both threads exit in parallel. They
    both can see tsk->signal->live == 2 before atomic_dec_and_test().

    If you are fine with this race I won't object, but please add a comment.

    But why can't you simply do

    --- x/kernel/exit.c
    +++ x/kernel/exit.c
    @@ -786,6 +786,8 @@ void __noreturn do_exit(long code)
    acct_update_integrals(tsk);
    group_dead = atomic_dec_and_test(&tsk->signal->live);
    if (group_dead) {
    + if (unlikely(is_global_init(tsk)
    + panic(...);
    #ifdef CONFIG_POSIX_TIMERS
    hrtimer_cancel(&tsk->signal->real_timer);
    exit_itimers(tsk->signal);

    ?

    Oleg.

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