linux-kernel - Re: [RFC v2 3/6] kthread: warn on kill signal if not OOM

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Date:	Fri, 5 Sep 2014 09:44:05 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Wu Zhangjin <falcon@...zu.com>, Takashi Iwai <tiwai@...e.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>, hare@...e.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Joseph Salisbury <joseph.salisbury@...onical.com>,
	Benjamin Poirier <bpoirier@...e.de>,
	Santosh Rastapur <santosh@...lsio.com>,
	Kay Sievers <kay@...y.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Tim Gardner <tim.gardner@...onical.com>,
	Pierre Fersing <pierre-fersing@...rref.org>,
	Nagalakshmi Nandigama <nagalakshmi.nandigama@...gotech.com>,
	Praveen Krishnamoorthy <praveen.krishnamoorthy@...gotech.com>,
	Sreekanth Reddy <sreekanth.reddy@...gotech.com>,
	Abhijit Mahajan <abhijit.mahajan@...gotech.com>,
	Casey Leedom <leedom@...lsio.com>,
	Hariprasad S <hariprasad@...lsio.com>,
	MPT-FusionLinux.pdl@...gotech.com,
	Linux SCSI List <linux-scsi@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC v2 3/6] kthread: warn on kill signal if not OOM

On Friday, September 05, 2014 11:12:41 PM Tejun Heo wrote:
> On Fri, Sep 05, 2014 at 12:47:16AM -0700, Luis R. Rodriguez wrote:
> > Ah -- well without it the way we "find" drivers that need this new
> > "async feature" is by a bug report and folks saying their system can't
> > boot, or they say their device doesn't come up. That's all. Tracing
> > this to systemd and a timeout was one of the most ugliest things ever.
> > There two insane bug reports you can go check:
> > 
> > mptsas was the first:
> > 
> > http://article.gmane.org/gmane.linux.kernel/1669550
> > https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1297248
> > 
> > Then cxgb4:
> > 
> > https://bugzilla.novell.com/show_bug.cgi?id=877622
> > 
> > I only had Cc'd you on the newest gem pata_marvell :
> > 
> > https://bugzilla.kernel.org/show_bug.cgi?id=59581
> > 
> > We can't seriously expect to be doing all this work for every driver.
> > a WARN_ONCE() would enable us to find the drivers that need this new
> > async probe "feature".
> 
> This whole approach of trying to mark specific drivers as needing
> "async probing" is completely broken for the problem at hand.  It
> can't address the problem adequately while breaking backward
> compatibility.  I don't think this makes much sense.
> 

Which problem are we talking about here though? It does solve the slow device
stalling the rest if the kernel booting (non-module case) for me.

I also reject the notion that anyone should be relying on drivers to be fully
bound on module loading. It is not nineties anymore. We have hot pluggable
buses, deferred probing, and even for not hot-pluggable ones the module
providing the device itself might not be yet loaded. Any scripts that expect to
find device 100% ready after module loading are simply broken.

Thanks.

-- 
Dmitry
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