linux-kernel - Re: [PATCH v3 20/21] dyndbg: add user-flag, negating-flags, and filtering on flags

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Message-ID: <CAJfuBxzrOinpvkYYPZ5fCMSRwTggYGRs0VxMhrm=AO-L5fuMRg@mail.gmail.com>
Date:   Thu, 18 Jun 2020 12:15:16 -0600
From:   jim.cromie@...il.com
To:     Petr Mladek <pmladek@...e.com>
Cc:     Jason Baron <jbaron@...mai.com>,
        LKML <linux-kernel@...r.kernel.org>, akpm@...uxfoundation.org,
        Greg KH <gregkh@...uxfoundation.org>,
        Rasmus Villemoes <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 Documentation List <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v3 20/21] dyndbg: add user-flag, negating-flags, and
 filtering on flags

On Thu, Jun 18, 2020 at 10:19 AM Petr Mladek <pmladek@...e.com> wrote:
>
> On Wed 2020-06-17 10:25:35, Jim Cromie wrote:


OK.
Please tell me how this chunk of prose fails to explain a use case for
the u-flag
we can differ on how useful it looks.

if u-flag is useful, then filtering on flags is also needed,
to use the flag to enable/disable an arbitrary set of callsites

all the other "flag abuse" you disliked in last patch is avoidable,
unless 2 people are chasing 2 separate problems,
and need to keep their sets distinct

> > Why ?
> >
> > The u-flag & filter flags
> >
> > The 'u' flag lets the user assemble an arbitary set of callsites.
> > Then using filter flags, user can activate the 'u' callsite set.
> >
> >   #> echo 'file foo.c +u; file bar.c +u' > control   # and repeat
> >   #> echo 'u+p' > control
> >
> > Of course, you can continue to just activate your set without ever
> > marking it 1st, but you could trivially add the markup as you go, then
> > be able to use it as a constraint later, to undo or modify your set.
> >
> >   #> echo 'file foo.c +up' >control
> >   .. monitor, debug, finish ..
> >   #> echo 'u-p' >control
> >
> >   # then later resume
> >   #> echo 'u+p' >control
> >
> >   # disable some cluttering messages, and remove from u-set
> >   #> echo 'file noisy.c function:jabber_* u-pu' >control
> >
> >   # for doc, recollection
> >   grep =pu control > my-favorite-callsites
> >
> > Note:
> >
> > Your flagstate after boot is generally not all =_. -DDEBUG will arm
> > compiled callsites by default, $builtinmod.dyndbg=+p bootargs can
> > enable them early, and $module.dyndbg=+p bootargs will arm them when
> > the module is loaded.  But you could manage them with u-flags:
> >
> >   #> echo '-t' >control               # clear t-flag to use it as 2ndary markup
> >   #> echo 'p+ut' >control     # mark the boot-enabled set of callsites
> >   #> echo '-p' >control               # clean your dmesg -w stream
> >
> >   ... monitor, debug ..
> >   #> echo 'module of_interest $qterms +pu' >control   # build your set of useful debugs
> >   #> echo 'module of_interest $qterms UT+pu' >control # same, but dont alter ut marked set
>
> Does anyone requested this feature, please?
>
> For me, it is really hard to imagine people using these complex and hacky
> steps.
>
> Not to say that using t-flag as a markup looks like a real hack.
> People either always need the line number in the kernel log or
> they do not need it at all.
>
> Let me repeat. Please, stop this non-sense.
>
> Best Regards,
> Petr