From: Petr Mladek <pmladek@suse.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
lijiang <lijiang@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrea Parri <parri.andrea@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] printk: replace ringbuffer
Date: Mon, 17 Feb 2020 15:50:16 +0100 [thread overview]
Message-ID: <20200217145016.7r6b7i5o6tqkaa2x@pathway.suse.cz> (raw)
In-Reply-To: <87blpxbh62.fsf@linutronix.de>
On Mon 2020-02-17 12:13:25, John Ogness wrote:
> On 2020-02-14, Petr Mladek <pmladek@suse.com> wrote:
> >> I oversaw that devkmsg_open() setup a printk_record and so I did not
> >> see to add the extra NULL initialization of text_line_count. There
> >> should be be an initializer function/macro to avoid this danger.
> >>
> >> John Ogness
> >>
> >> The quick fixup:
> >>
> >> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> >> index d0d24ee1d1f4..5ad67ff60cd9 100644
> >> --- a/kernel/printk/printk.c
> >> +++ b/kernel/printk/printk.c
> >> @@ -883,6 +883,7 @@ static int devkmsg_open(struct inode *inode, struct file *file)
> >> user->record.text_buf_size = sizeof(user->text_buf);
> >> user->record.dict_buf = &user->dict_buf[0];
> >> user->record.dict_buf_size = sizeof(user->dict_buf);
> >> + user->record.text_line_count = NULL;
> >
> > The NULL pointer hidden in the structure also complicates the code
> > reading. It is less obvious when the same function is called
> > only to get the size/count and when real data.
>
> OK.
>
> > I played with it and created extra function to get this information.
> >
> > In addition, I had problems to follow the code in
> > record_print_text_inline(). So I tried to reuse the new function
> > and the existing record_printk_text() there.
> >
> > Please, find below a patch that I ended with. I booted a system
> > with this patch. But I guess that I actually did not use the
> > record_print_text_inline(). So, it might be buggy.
>
> Yes, there are several bugs. But I see where you want to go with this:
>
> - introduce prb_count_lines() to handle line counting
>
> - introduce prb_read_valid_info() for only reading meta-data and getting
> the line count
>
> - also use prb_count_lines() internally
In addition, I would like share the code between
record_print_text_inline() and record_print_text().
They both do very similar thing and the logic in far from
trivial.
Alternative solution would be to get rid of record_print_text()
and use record_print_text_inline() everywhere. It will have some
advantages:
+ _inline() variant will get real testing
+ no code duplication
+ saving the extra buffer also in console, sysfs, and devkmsg interface.
> I will include these changes in v2. I will still introduce the static
> inlines to initialize records because readers and writers do it
> differently.
Sounds good.
Best Regards,
Petr
next prev parent reply other threads:[~2020-02-17 14:50 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-28 16:19 [PATCH 0/2] printk: replace ringbuffer John Ogness
2020-01-28 16:19 ` [PATCH 1/2] printk: add lockless buffer John Ogness
2020-01-29 3:53 ` Steven Rostedt
2020-02-21 11:54 ` more barriers: " Petr Mladek
2020-02-27 12:04 ` John Ogness
2020-03-04 15:08 ` Petr Mladek
2020-03-13 10:13 ` John Ogness
2020-02-21 12:05 ` misc nits " Petr Mladek
2020-03-02 10:38 ` John Ogness
2020-03-02 12:17 ` Joe Perches
2020-03-02 12:32 ` Petr Mladek
2020-03-02 13:43 ` John Ogness
2020-03-03 9:47 ` Petr Mladek
2020-03-03 15:42 ` John Ogness
2020-03-04 10:09 ` Petr Mladek
2020-03-04 9:40 ` Petr Mladek
2020-01-28 16:19 ` [PATCH 2/2] printk: use the lockless ringbuffer John Ogness
2020-02-13 9:07 ` Sergey Senozhatsky
2020-02-13 9:42 ` John Ogness
2020-02-13 11:59 ` Sergey Senozhatsky
2020-02-13 22:36 ` John Ogness
2020-02-14 1:41 ` Sergey Senozhatsky
2020-02-14 2:09 ` Sergey Senozhatsky
2020-02-14 9:48 ` John Ogness
2020-02-14 13:29 ` lijiang
2020-02-14 13:50 ` John Ogness
2020-02-15 4:15 ` lijiang
2020-02-17 15:40 ` crashdump: " Petr Mladek
2020-02-17 16:14 ` John Ogness
2020-02-17 14:41 ` misc details: " Petr Mladek
2020-02-25 20:11 ` John Ogness
2020-02-26 9:54 ` Petr Mladek
2020-02-05 4:25 ` [PATCH 0/2] printk: replace ringbuffer lijiang
2020-02-05 4:42 ` Sergey Senozhatsky
2020-02-05 4:48 ` Sergey Senozhatsky
2020-02-05 5:02 ` Sergey Senozhatsky
2020-02-05 5:38 ` lijiang
2020-02-05 6:36 ` Sergey Senozhatsky
2020-02-05 9:00 ` John Ogness
2020-02-05 9:28 ` Sergey Senozhatsky
2020-02-05 10:19 ` lijiang
2020-02-05 16:12 ` John Ogness
2020-02-06 9:12 ` lijiang
2020-02-13 13:07 ` Petr Mladek
2020-02-14 1:07 ` Sergey Senozhatsky
2020-02-05 11:07 ` Sergey Senozhatsky
2020-02-05 15:48 ` John Ogness
2020-02-05 19:29 ` Joe Perches
2020-02-06 6:31 ` Sergey Senozhatsky
2020-02-06 7:30 ` lijiang
2020-02-07 1:40 ` Steven Rostedt
2020-02-07 7:43 ` John Ogness
2020-02-14 15:56 ` Petr Mladek
2020-02-17 11:13 ` John Ogness
2020-02-17 14:50 ` Petr Mladek [this message]
2020-02-25 19:27 ` John Ogness
2020-02-05 9:36 ` lijiang
2020-02-06 9:21 ` lijiang
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