linux-kernel - Re: sched: serial port lockdep warning when offlining CPUs

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Date:   Thu, 28 Sep 2017 20:51:18 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sasha Levin <levinsasha928@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        alexander.levin@...izon.com, pmladek@...e.com,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org
Subject: Re: sched: serial port lockdep warning when offlining CPUs

On (09/28/17 13:47), Peter Zijlstra wrote:
> On Thu, Sep 28, 2017 at 07:30:32PM +0900, Sergey Senozhatsky wrote:
> > ---
> > 
> >  lib/ratelimit.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/lib/ratelimit.c b/lib/ratelimit.c
> > index 08f8043cac61..bddc55834c2e 100644
> > --- a/lib/ratelimit.c
> > +++ b/lib/ratelimit.c
> > @@ -48,7 +48,8 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
> >  	if (time_is_before_jiffies(rs->begin + rs->interval)) {
> >  		if (rs->missed) {
> >  			if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
> > -				pr_warn("%s: %d callbacks suppressed\n", func, rs->missed);
> > +				printk_deferred(KERN_WARN "%s: %d callbacks suppressed\n",
> > +						func, rs->missed);
> >  				rs->missed = 0;
> >  			}
> >  		}
> 
> Oh cute; I figured it was the syslog daemon suppressing multiple
> identical lines, but yes the above looks very plausible.

seems to be stable v4.8+ material.

Fixes: 6b1d174b0c27b ("ratelimit: extend to print suppressed messages on release")

I'll send out a patch.

	-ss