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Groups > linux.kernel > #1722967

Re: printk: what is going on with additional newlines?

From Joe Perches <joe@perches.com>
Newsgroups linux.kernel
Subject Re: printk: what is going on with additional newlines?
Date 2017-08-30 04:00 +0200
Message-ID <uk0sp-1Us-1@gated-at.bofh.it> (permalink)
References (6 earlier) <ujSbw-5nB-15@gated-at.bofh.it> <ujSlb-5rP-11@gated-at.bofh.it> <ujYAi-LM-9@gated-at.bofh.it> <ujZG1-1EU-9@gated-at.bofh.it> <ujZPH-1HW-7@gated-at.bofh.it>
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On Tue, 2017-08-29 at 21:10 -0400, Steven Rostedt wrote:
> 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.

No need.  printk would already add timestamps.

One addition might be to add a bit to initialize
the buffer so that printk("%s", s->buffer) is simpler.
---
diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index fb7eb9ccb1cd..fb6c9de0ee33 100644
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h
@@ -26,6 +26,7 @@ static inline void seq_buf_clear(struct seq_buf *s)
 {
 	s->len = 0;
 	s->readpos = 0;
+	*s->buffer = 0;
 }
 
 static inline void

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Thread

printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-08-28 11:10 +0200
  Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-28 12:30 +0200
    Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-28 14:30 +0200
      Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-28 14:40 +0200
      Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-08-28 14:50 +0200
        Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-29 15:50 +0200
          Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 18:40 +0200
          Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:10 +0200
            Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:20 +0200
              Re: printk: what is going on with additional newlines? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-08-29 22:50 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 23:00 +0200
                Re: printk: what is going on with additional newlines? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-02 08:20 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-02 19:10 +0200
              Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-08-30 02:00 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-30 02:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:10 +0200
                Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-08-30 03:20 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:50 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-30 04:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 04:30 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-30 04:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 04:50 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-30 05:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 07:40 +0200
                Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-09-08 12:20 +0200
                Re: printk: what is going on with additional newlines? Petr Mladek <pmladek@suse.com> - 2017-09-05 11:50 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-05 12:10 +0200
                Re: printk: what is going on with additional newlines? Petr Mladek <pmladek@suse.com> - 2017-09-05 14:30 +0200
                Re: printk: what is going on with additional newlines? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-05 14:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-05 16:30 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-05 15:50 +0200
                Re: printk: what is going on with additional newlines? Petr Mladek <pmladek@suse.com> - 2017-09-06 10:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-01 15:30 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-01 19:40 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-01 22:30 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-04 07:30 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-04 07:50 +0200
                Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-09-05 17:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-06 04:20 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-06 04:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-04 06:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-04 07:30 +0200
            Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-08-29 19:40 +0200
              Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 20:00 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 20:10 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:10 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:00 +0200
  Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 18:50 +0200
    Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 19:20 +0200
      Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:30 +0200
        Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 19:40 +0200
          Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:40 +0200
            Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 19:50 +0200
    Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-08-29 22:30 +0200
      Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-01 03:50 +0200
        Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-01 04:10 +0200
          Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-09-01 09:00 +0200
            Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-01 09:30 +0200
        Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-09-01 09:30 +0200
          Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-09-01 13:20 +0200

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