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    SubjectRe: [BUG] 8e274732115f ("printk: extend console_lock for per-console locking")
    On Mon, Jun 13, 2022 at 11:10:19AM +0206, John Ogness wrote:
    > On 2022-06-12, "Paul E. McKenney" <paulmck@kernel.org> wrote:
    > >> As I suspected, the final printk's cannot direct print because the
    > >> kthread was printing. Using the below patch did seem to address your
    > >> problem. But this is probably not the way forward.
    > >
    > > When I apply it, I still lose output, perhaps due to different timing?
    > > Doing the pr_flush(1000, true) just before the call to kernel_power_off()
    > > has been working quite well thus far, though.
    >
    > Your pr_flush() is appropriate for your RCU tests, but this is a problem
    > in general that needs to be addressed. I suppose we should start a new
    > thread for that. ;-)
    >
    > During development we experimented with the idea of kthreads pausing
    > themselves whenever direct printing is activated. It was racey because
    > there are situations when direct printing is only temporarily active and
    > it was hard to coordinate who prints when direct printing becomes
    > inactive again. So we dropped that idea. However, in this situation the
    > system will not be disabling direct printing.
    >
    > @Paul, can you try the below change instead? Until this has been
    > officially solved, you probably want to keep your pr_flush()
    > solution. (After all, that is exactly what pr_flush() is for.) But it
    > would be helpful if you could run this last test for us.
    >
    > @Petr, I like the idea of the kthreads getting out of the way rather
    > than trying to direct print themselves (for this situation). It still
    > isn't optimal because that final pr_emerg("Power down\n") might come
    > before the kthread has finished its current line. But in that case the
    > kthread may not have much a chance to finish the printing anyway.
    >
    > John Ogness
    >
    > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
    > index ea3dd55709e7..45c6c2b0b104 100644
    > --- a/kernel/printk/printk.c
    > +++ b/kernel/printk/printk.c
    > @@ -3729,7 +3729,9 @@ static bool printer_should_wake(struct console *con, u64 seq)
    > return true;
    >
    > if (con->blocked ||
    > - console_kthreads_atomically_blocked()) {
    > + console_kthreads_atomically_blocked() ||
    > + system_state > SYSTEM_RUNNING ||
    > + oops_in_progress) {
    > return false;
    > }

    And this one works for me, thank you!!!

    On to Petr's patch...

    Thanx, Paul

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