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

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Message-ID: <20170928114528.wilknwkyjecqrcaa@sasha-lappy>
Date:   Thu, 28 Sep 2017 11:45:30 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
CC:     Sasha Levin <levinsasha928@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "sergey.senozhatsky@...il.com" <sergey.senozhatsky@...il.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>
Subject: Re: sched: serial port lockdep warning when offlining CPUs

On Thu, Sep 28, 2017 at 08:36:07PM +0900, Sergey Senozhatsky wrote:
>On (09/28/17 19:30), 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",
>
>oops...				s/KERN_WARN/KERN_WARNING/
>
>sorry about that.

Okay, that seems to have delt with the callbacks supressed issue.

I also seem to be hitting it as a result of the scheduler triggering a WARN, where print_stack_trace(), for example, just uses printk().

Now I'm not sure what's your approach here, do we keep converting printk to printk_deferred one by one until we whacked every mole?

-- 

Thanks,
Sasha