linux-kernel - Re: [PATCH v3 19/21] dyndbg: extend ddebug_parse_flags to accept optional leading filter-flags

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Date:   Thu, 18 Jun 2020 14:44:00 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Jim Cromie <jim.cromie@...il.com>
Cc:     jbaron@...mai.com, linux-kernel@...r.kernel.org,
        akpm@...uxfoundation.org, gregkh@...uxfoundation.org,
        linux@...musvillemoes.dk, Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Orson Zhai <orson.zhai@...soc.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 19/21] dyndbg: extend ddebug_parse_flags to accept
 optional leading filter-flags

On Wed 2020-06-17 10:25:34, Jim Cromie wrote:
> Change ddebug_parse_flags to accept optional filterflags before the
> required operator [-+=].  Read the flags into the filter_flags
> parameter added in the previous patch.  So this now supplies the
> filterflags to ddebug_exec_query.
> 
> filterflags work like query terms, they constrain what callsites get
> matched before theyre modified.  So like a query, they can be empty.
> 
> Filterflags let you read callsite's flagstate, including results of
> previous modifications, and require that certain flags are set, before
> modifying the callsite further.
> 
> So you can build up sets of callsites by marking them with a
> particular flagstate, for example 'fmlt', then enable that set in a
> batch.
> 
>   echo fmlt+p >control
> 
> Naturally you can use almost any combo of flags you want for marking,
> and can mark several different sets with different patterns.  And then
> you can activate them in a bunch:
> 
>   echo 'ft+p; mt+p; lt+p;' >control
> 
> + * Parse `str' as a flags-spec, ie: [pfmlt_]*[-+=][pfmlt_]+

This interface is simply _horrible_ and I do not see a point in this feature!!!

I as a normal dynamic debug user am interested into:

   + enabling/disabling messages from a given module/file/line/function
   + list of available modules/files/lines/functions
   + list of enabled modules/files/lines/functions

I do not understand why I would ever want to do something like:

   + enable messages that print module name and line number
   + disable message that does not print a module name

In fact, IMHO, all the 'flmt' flags were a wrong idea and nobody
really needed them. This information in not needed by other
printk() messages. Why pr_debug() would need them?
They just made the code and interface complicated.

Please, stop all this non-sense!!!

Best Regards,
Petr