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

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Message-ID: <20170830010348.GB654@jagdpanzerIV.localdomain>
Date:   Wed, 30 Aug 2017 10:03:48 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        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?

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.

	-ss