linux-kernel - Re: [PATCH] printk: kmsg_dump: Mark registered flag as private

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Date:   Tue, 12 Mar 2019 21:05:33 +0100
From:   "Ahmed S. Darwish" <darwish.07@...il.com>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: kmsg_dump: Mark registered flag as private

Hi,

On Mon, Mar 11, 2019 at 09:49:05PM +0900, Sergey Senozhatsky wrote:
> On (03/10/19 21:03), Ahmed S. Darwish wrote:
> > The 'registered' flag is internally used by kmsg_dump_register()
> > and kmsg_dump_unregister() to track multiple registrations of the
> > same dumper.
> >
> > It's protected by printk's internal dump_list_lock, and must thus
> > be accessed only from there. Mark it as private.
> >
> > Signed-off-by: Ahmed S. Darwish <darwish.07@...il.com>
> > ---
> >  include/linux/kmsg_dump.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
> > index 2e7a1e032c71..7c08cb58259a 100644
> > --- a/include/linux/kmsg_dump.h
> > +++ b/include/linux/kmsg_dump.h
> > @@ -36,7 +36,7 @@ enum kmsg_dump_reason {
> >   * @dump:	Call into dumping code which will retrieve the data with
> >   * 		through the record iterator
> >   * @max_reason:	filter for highest reason number that should be dumped
> > - * @registered:	Flag that specifies if this is already registered
> > + * @registered:	Flag that specifies if this is already registered (private)
> >   */
> >  struct kmsg_dumper {
> >  	struct list_head list;
>
>
> Do we really do this thing?
>
>
> $ git grep "(private)" include/linux/
> include/linux/kmsg_dump.h: * @list:     Entry in the dumper list (private)
> include/linux/uwb.h: * specific (private) DevAddr (UWB_RSV_TARGET_DEVADDR).
>

Hmmm, while writing a kmsg_dumper for [1], I noticed that struct
kmsg_dumper is:

    /**
     * struct kmsg_dumper - kernel crash message dumper structure
     * @list:        Entry in the dumper list (private)  <== *
     * ...
     * @registered:  Flag that specifies if this is already registered
     */
    struct kmsg_dumper {
    	struct list_head list;
    	...
    	bool registered;
    	/* private state of the kmsg iterator */         <== *
    	...
    };

_All_ private members are annotated (<== *), so this gave the
impression that 'bool registered' was public..

Then I discovered from printk.c code that it's actually private,
and protected by the printk's internal dump_list_lock...

So this trivial patch was submitted for consistency.

thanks,

[1] https://lore.kernel.org/lkml/20190310013142.GA3376@darwi-home-pc

--
darwi
http://darwish.chasingpointers.com