Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test_stage

[Sergey Senozhatsky]

On (04/09/17 12:12), Pavel Machek wrote:
[..]
> > a side note,
> > that's rather unclear to me how would "message delayed" really help.
> > if your system hard-lockup so badly and there are no printk messages
> > even from NMI watchdog, then we won't be able to print that message.
> 
> We are talking about
> 
>    printk("unusual condition");
>    do_something_clever(); /* Which unfortunately hard-crashes the machine */
> 
> that works with my proposal, but not with yours. Seen it happen many
> times before.

I see your point, sure.
I can't completely agree on "that works with my proposal, but not with yours."

on SMP system this would be true only if no other CPU holds the console_sem
at the time we call printk(). (skipping irrelevant cases when we have suspended
console or !online CPU and !CON_ANYTIME console). and there is nothing that
makes "no other CPU holds the console_sem" always true on SMP system at any
given point in time. so no, "A always works, B never works" is not accurate.

but, once again, I see your point.

	-ss