linux-kernel - Re: [RFC][PATCHv5 07/13] printk: register syscore notifier

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Date:   Wed, 16 Aug 2017 15:55:45 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>, Jan Kara <jack@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Pavel Machek <pavel@....cz>,
        Andreas Mohr <andi@...as.de>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCHv5 07/13] printk: register syscore notifier

On (08/15/17 13:56), Rafael J. Wysocki wrote:
[..]
> > +static int printk_syscore_suspend(void)
> > +{
> > +	printk_emergency_begin();
> > +	return 0;
> > +}
> 
> Somebody looking at suspend/resume code paths only will be wondering why
> you need this, because we should be in the emergency mode already when
> it is called.
> 
> It would be good to add a comment about the kexec context here.

ok, will add.

> > +static void printk_syscore_resume(void)
> > +{
> > +	printk_emergency_end();
> > +}
> 
> This will turn the emergency mode off during resume before the notifier
> added by the previous patch AFAICS.  Is this intentional?

emergency modes can nest. so it's OK to have

	printk_emergency_begin()   +1   // on
	  printk_emergency_begin()   +1
	  printk_emergency_end()     -1
	printk_emergency_end()     -1   // off

or did I misunderstand your question?

	-ss