[PATCH 2/4] printk: store instead of processing cont parts

[John Ogness]

On 2020-07-21, Sergey Senozhatsky <sergey.senozhatsky at gmail.com> wrote:
>> That said, we have traditionally used not just "current process", but
>> also "last irq-level" as the context information, so I do think it
>> would be good to continue to do that.
>
> OK, so basically, extending printk_caller_id() so that for IRQ/NMI
> we will have more info than just "0x80000000 + raw_smp_processor_id()".

If bit31 is set, the upper 8 bits could specify what the lower 24 bits
represent. That would give some freedom for the future.

For example:

0x80 = cpu id (generic context)
0x81 = interrupt number
0x82 = cpu id (nmi context)

Or maybe ascii should be used instead?

0x80 | '\0' = cpu id (generic context)
0x80 | 'i'  = interrupt number
0x80 | 'n'  = cpu id (nmi context)

Just an idea.

John Ogness