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Date: Tue, 4 Apr 2017 18:36:45 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>, Jan Kara <jack@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Eric Biederman <ebiederm@xmission.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>, Pavel Machek <pavel@ucw.cz>,
        Len Brown <len.brown@intel.com>, linux-kernel@vger.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCHv2 2/8] printk: introduce printing kernel thread
Message-ID: <20170404093645.GD470@jagdpanzerIV.localdomain>
References: <20170329092511.3958-1-sergey.senozhatsky@gmail.com>
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 <20170404090120.GH29537@pathway.suse.cz>
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On (04/04/17 11:01), Petr Mladek wrote:
[..]
> > +static atomic_t printk_emergency __read_mostly;
> > +/*
> > + * Disable printk_kthread permanently. Unlike `oops_in_progress'
> > + * it doesn't go back to 0.
> > + */
> 
> The comment is not valid once we allow to modify the variable using
> the sysfs knob.

it's updated in that patch (sysfs knob introduction).


[..]
> > @@ -2182,6 +2253,7 @@ void console_unlock(void)
> >  	console_may_schedule = 0;
> >  
> >  again:
> > +	clear_bit(PRINTK_PENDING_OUTPUT, &printk_pending);
> 
> This will not help if new messages appear during
> call_console_drivers().

you are right. wouldn't do much harm (an extra console_unlock() from
printk_kthread in the worst case), but agree.

I added it there because of that "!can_use_console()" branch. not that
I expect printk_kthread being executed on !online CPU, but we might have
no callable consoles.

probably should have that clear_bit() before and after the loop.

	-ss