linux-kernel - Re: [RFC][PATCHv2 5/8] sysrq: switch to printk.emergency mode in unsafe places

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Message-ID: <20170401000450.GB478@tigerII.localdomain>
Date:   Sat, 1 Apr 2017 09:04:50 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>, Jan Kara <jack@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Eric Biederman <ebiederm@...ssion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Pavel Machek <pavel@....cz>,
        Len Brown <len.brown@...el.com>, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCHv2 5/8] sysrq: switch to printk.emergency mode in
 unsafe places

Hello,

On (03/31/17 17:37), Petr Mladek wrote:
> On Wed 2017-03-29 18:25:08, Sergey Senozhatsky wrote:
> > It's not always possible/safe to wake_up() printk kernel
> > thread from sysrq (theoretically). Thus we better switch
> > printk() to emergency mode in some of the sysrq handlers,
> > which allows us to immediately flush pending kernel message
> > to the console.
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> > Suggested-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> 
> It looks like a decent selection. It is pity that some of
> them might produce rather long output and theoretically
> cause a softlookup. But I do not know about a better solution
> at the moment. In each case, it will not be worse than before
> this patchset.

thanks.

this patch will be replaced with a more 'generic' one, which
I posted in reply yo Ye Xiaolong's report.

	-ss