linux-kernel - Re: [PATCH 1/2] genirq/cpuhotplug: Reduce logging level for couple of prints

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Message-ID: <87zh5f6o9t.fsf@nanos.tec.linutronix.de>
Date:   Thu, 24 Sep 2020 20:08:30 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Prasad Sodagudi <psodagud@...eaurora.org>, rostedt@...dmis.org,
        pmladek@...e.com, sergey.senozhatsky@...il.com,
        gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org, tkjos@...gle.com,
        Prasad Sodagudi <psodagud@...eaurora.org>
Subject: Re: [PATCH 1/2] genirq/cpuhotplug: Reduce logging level for couple of prints

On Wed, Sep 23 2020 at 17:08, Prasad Sodagudi wrote:
> During the cpu hot plug stress testing, couple of messages
> continuous flooding on to the console is causing timers
> migration delay. Delayed time migrations from hot plugging
> core is causing device instability with watchdog. So reduce
> log level for couple of prints in cpu hot plug flow.

This is fixing the wrong end, really.

Timer migration can be delayed by other means as well.

The real problem is that the migration happens _after_ the CPU is
completely dead and the hotplug control thread is not guaranteed to
reach the timer migration state before timers are overdue at all.

There is a bunch of related problems, e.g. the interrupt migration
mechanism kicks in late as well.

I'm not against changing the log level per se, but the justification for
doing so is just bogus.

The more obvious question is whether these printks are useful at all
other than at the pr_debug() level.

Thanks,

        tglx