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    SubjectRe: [PATCH printk v5 1/1] printk: extend console_lock for per-console locking
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    Hi John,

    On 02.05.2022 15:11, John Ogness wrote:
    > On 2022-05-02, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
    >> Data written to /dev/kmsg and all kernel logs were always displayed
    >> correctly. Also data written directly to /dev/ttyAML0 is displayed
    >> properly on the console. The latter doesn't however trigger the input
    >> related activity.
    >>
    >> It looks that the data read from the uart is delivered only if other
    >> activity happens on the kernel console. If I type 'reboot' and press
    >> enter, nothing happens immediately. If I type 'date >/dev/ttyAML0' via
    >> ssh then, I only see the date printed on the console. However if I
    >> type 'date >/dev/kmsg', the the date is printed and reboot happens.
    > I suppose if you login via ssh and check /proc/interrupts, then type
    > some things over serial, then check /proc/interrupts again, you will see
    > there have been no interrupts for the uart. But interrupts for other
    > devices are happening. Is this correct?

    Right. The counter for ttyAML0 is not increased when lockup happens and
    I type something to the uart console.

    >> For comparison, here is a 't' sysrq result from the 'working' serial
    >> console (next-20220429), which happens usually 1 of 4 boots:
    >>
    >> https://protect2.fireeye.com/v1/url?k=3ef0fd63-5f7be855-3ef1762c-000babff9b5d-2e40dc5adc30a14c&q=1&e=1469838f-8586-403e-bd4d-922675d8b658&u=https%3A%2F%2Fpastebin.com%2Fmp8zGFbW
    > This still looks odd to me. We should be seeing a trace originating from
    > ret_from_fork+0x10/0x20 and kthread+0x118/0x11c.
    >
    > I wonder if the early creation of the thread is somehow causing
    > problems. Could you try the following patch to see if it makes a
    > difference? I would also like to see the sysrq-t output with this patch
    > applied:
    >
    > ---------------- BEGIN PATCH ---------------
    > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
    > index 2311a0ad584a..c4362d25de22 100644
    > --- a/kernel/printk/printk.c
    > +++ b/kernel/printk/printk.c
    > @@ -3837,7 +3837,7 @@ static int __init printk_activate_kthreads(void)
    >
    > return 0;
    > }
    > -early_initcall(printk_activate_kthreads);
    > +late_initcall(printk_activate_kthreads);
    >
    > #if defined CONFIG_PRINTK
    > /* If @con is specified, only wait for that console. Otherwise wait for all. */
    > ---------------- END PATCH ---------------
    >
    > Thanks for your help with this!

    Well, nothing has changed. The lockup still happens.

    Best regards
    --
    Marek Szyprowski, PhD
    Samsung R&D Institute Poland

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