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Date: Tue, 29 Aug 2017 21:10:46 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Pavel Machek <pavel@ucw.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Petr Mladek <pmladek@suse.com>, Jan Kara <jack@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jiri Slaby <jslaby@suse.com>, Andreas Mohr <andi@lisas.de>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: printk: what is going on with additional newlines?
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On Wed, 30 Aug 2017 10:03:48 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:

> Hello,
> 
> On (08/29/17 19:50), Steven Rostedt wrote:
> [..]
> > > A private buffer has none of those issues.  
> > 
> > What about using the seq_buf*() then?
> > 
> > 	struct seq_buf s;
> > 
> > 	buf = kmalloc(mysize);
> > 	seq_buf_init(&s, buf, mysize);
> > 
> > 	seq_printf(&s,"blah blah %d", bah_blah);
> > 	[...]
> > 	seq_printf(&s, "my last print\n");
> > 
> > 	printk("%.*s", s.len, s.buffer);
> > 
> > 	kfree(buf);  
> 
> could do. for a single continuation line printk("%.*s", s.len, s.buffer)
> this will work perfectly fine. for a more general case - backtraces, dumps,
> etc. - this requires some tweaks.

We could simply add a seq_buf_printk() that is implemented in the printk
proper, to parse the seq_buf buffer properly, and add the timestamps and
such.

-- Steve