linux-kernel - Re: [printk] b031a684bf: INFO:rcu_tasks_detected_stalls_on

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Date:   Thu, 28 Jan 2021 17:30:02 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        kernel test robot <oliver.sang@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        lkp@...el.com, zhengjun.xing@...ux.intel.com
Subject: Re: [printk]  b031a684bf: INFO:rcu_tasks_detected_stalls_on_tasks

On (21/01/27 22:28), John Ogness wrote:
> 
> # modprobe rcutorture onoff_interval=3 onoff_holdoff=30 torture_type=tasks
> 
> (Those are the same modprobe parameters used by the lkp job.)
> 
> After about a minute I see:
> 
> [   47.268292] tasks-torture: rcu_torture_read_exit: Start of episode
> [   51.273365] tasks-torture: rcu_torture_read_exit: End of episode
> [   55.823306] smpboot: do_boot_cpu failed(-1) to wakeup CPU#0
> [   55.824350] tasks-torture:torture_onoff task: online 0 failed: errno -5
> [   55.830661] tasks-torture:torture_onoff task: online 0 failed: errno -5
> [   55.848524] tasks-torture:torture_onoff task: online 0 failed: errno -5

Just out of curious, this is seen only with the printk commit in
question applied? do_boot_cpu() doesn't seem to call a lot of printk-s,
only pr_debug("Setting warm reset code and vector.\n"), as far as I can
tell.

I can't repro this on my arm64 board. Maybe it's too slow. Race condition?

	-ss