linux-kernel - Re: printk: what is going on with additional newlines?

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Date:   Tue, 29 Aug 2017 21:10:46 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Pavel Machek <pavel@....cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>, Jan Kara <jack@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jiri Slaby <jslaby@...e.com>, Andreas Mohr <andi@...as.de>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: printk: what is going on with additional newlines?

On Wed, 30 Aug 2017 10:03:48 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@...il.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