From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [RFC v2 3/6] kthread: warn on kill signal if not OOM
Date: Tue, 9 Sep 2014 10:10:59 +0900
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Cc: Lennart Poettering <lennart@poettering.net>,
	Kay Sievers <kay@vrfy.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Wu Zhangjin <falcon@meizu.com>, Takashi Iwai <tiwai@suse.de>,
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	Oleg Nesterov <oleg@redhat.com>, hare@suse.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Joseph Salisbury <joseph.salisbury@canonical.com>,
	Benjamin Poirier <bpoirier@suse.de>,
	Santosh Rastapur <santosh@chelsio.com>,
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	Tim Gardner <tim.gardner@canonical.com>,
	Pierre Fersing <pierre-fersing@pierref.org>,
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	Praveen Krishnamoorthy <praveen.krishnamoorthy@avagotech.com>,
	Sreekanth Redd
To: "Luis R. Rodriguez" <mcgrof@do-not-panic.com>
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Hello, Luis.

On Mon, Sep 08, 2014 at 06:04:23PM -0700, Luis R. Rodriguez wrote:
> > I have no idea how the selection should be.  It could be per-insmod or
> > maybe just a system-wide flag with explicit exceptions marked on
> > drivers is good enough.  I don't know.
> 
> Its perfectly understandable if we don't know what path to take yet
> and its also understandable for it to take time to figure out --
> meanwhile though systemd already has merged a policy of a 30 second
> timeout for *all drivers* though so we therefore need:

I'm not too convinced this is such a difficult problem to figure out.
We already have most of logic in place and the only thing missing is
how to switch it.  Wouldn't something like the following work?

* Add a sysctl knob to enable asynchronous device probing on module
  load and enable asynchronous probing globally if the knob is set.

* Identify cases which can't be asynchronous and make them
  synchronous.  e.g. keep who's doing request_module() and avoid
  asynchronous probing if current is probing one of those.

Thanks.

-- 
tejun