Re: [PATCH v3 6/7] venus: Make debug infrastructure more flexible

jim.cromie
2020-06-12T00:09:26Z

calling out some thinkos

On Thu, Jun 11, 2020 at 3:19 PM <jim.cromie@gmail.com> wrote:
>
> heres what I have in mind. whats described here is working.
> I'll send it out soon
>
> commit 20298ec88cc2ed64269c8be7b287a24e60a5347e
> Author: Jim Cromie <jim.cromie@gmail.com>
> Date: Wed Jun 10 12:55:08 2020 -0600
>
> dyndbg: WIP towards module->debugflags based callsite controls
>
> There are *lots* of ad-hoc debug printing solutions in kernel,
> this is a 1st attempt at providing a common mechanism for many of them.
>
> Basically, there are 2 styles of debug printing:
> - levels, with increasing verbosity, 1-10 forex
> - bits/flags, independently controlling separate groups of dprints
>
> This patch does bits/flags (with no distinction made yet between 2)
>
> API:
>
> - change pr_debug(...) --> pr_debug_typed(type_id=0, ...)

pr_debug, pr_debug_n now in printk.h

_?_?dynamic_.+_cl adaptations in dynamic_debug.h

> - all existing uses have type_id=0
> - developer creates exclusive types of log messages with type_id>0
> 1, 2, 3 are disjoint groups, for example: hi, mid, low
>
> - !!type_id is just an additional callsite selection criterion
>
> Qfoo() { echo module foo $* >/proc/dynamic_debug/control }
> Qfoo +p # all groups, including default 0
> Qfoo mflags 1 +p # only group 1
> Qfoo mflags 12 +p # TBD[1]: groups 1 or 2
> Qfoo mflags 0 +p # ignored atm TBD[2]
> Qfoo mflags af +p # TBD[3]: groups a or f (10 or 15)
>
> so patch does:
>
> - add u32 debugflags to struct module. Each bit is a separate print-class.

this is feeling wrong now.
setting these bits would have to trigger an update via ddebug_exec_query
kinda like setting a bit would trigger
echo module $foo mflags $bitpos +p > control

its possible, but not 1st, or 2nd perhaps.
In general Im quite leery of rigging up some callback to do it.

its prudent to effect all debug changes via >control

> - in ddebug_change()
> filter on !! module->debugflags,
> IFF query->module is given, and matches dt->mod_name
> and query->mflags is given, and bitmatches module->debugflags

wrong, ddebug_change cannot respond to changes of debugflags,
most it could do is consult it on queries

> - in parse_query()
> accept new query term: mflags $arg
> populate query->mflags
> arg-type needs some attention, but basic plumbing is there
>
> WIP: not included:
>
> - pr_debug_typed( bitpos=0, ....)'

now done, as pr_debug_n, pr_debug in printk.h

Ive adapted the macros with a "_cl(cl, " insertion,

also added trailing prcls to control output

>
> - no way to exersize new code in ddebug_change
> need pr_debug_typed() to make a (not-null) typed callsite.
> also no way to set module->debugflags

close enough to see the thinkos