Messages in this thread | | | Date | Tue, 3 May 2022 00:29:00 +0200 | Subject | Re: [PATCH printk v5 1/1] printk: extend console_lock for per-console locking | From | Marek Szyprowski <> |
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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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