linux-kernel - Re: please fix FUSION (Was:[v3.13][v3.14][Regression]kthread:makekthread

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Date:	Sun, 23 Mar 2014 09:04:22 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
cc:	oleg@...hat.com, joseph.salisbury@...onical.com,
	JBottomley@...allels.com, Nagalakshmi.Nandigama@....com,
	Sreekanth.Reddy@....com, rientjes@...gle.com,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	tj@...nel.org, linux-kernel@...r.kernel.org,
	kernel-team@...ts.ubuntu.com, linux-scsi@...r.kernel.org,
	thenzl@...hat.com
Subject: Re: please fix FUSION
 (Was:[v3.13][v3.14][Regression]kthread:makekthread_create()killable)

On Sun, 23 Mar 2014, Tetsuo Handa wrote:

> Thomas Gleixner wrote:
> > But then systemd/udev mutters:
> > 
> >    "You migh be able to work around the timeout with udev rules and
> >     OPTIONS+="event_timeout=120", but that code was maybe never used
> >     or tested, so it might not work correctly." [1]
> > 
> > AFAICT from the ubuntu bug system [2] nobody bothered even to try that.
> > 
> > And if the udev/systemd event_timeout option is broken it's way better
> > to fix that one instead of hacking random heuristics into the kernel.
> 
> I haven't tried the event_timeout= option but I think it will not work.
> The timeout is hard coded as shown below and there will be no chance for taking
> the event_timeout= option into account.
> 
> ---------- systemd-204/src/udev/udevd.c start ----------
> (...snipped...)
>                         /* check for hanging events */
>                         udev_list_node_foreach(loop, &worker_list) {
>                                 struct worker *worker = node_to_worker(loop);
> 
>                                 if (worker->state != WORKER_RUNNING)
>                                         continue;
> 
>                                 if ((now(CLOCK_MONOTONIC) - worker->event_start_usec) > 30 * 1000 * 1000) {

And because systemd has an immutable hardcoded random timeout we add
another hardcoded random timeout into kthread_create() to work around
that.

How broken is that?

And it seems other people have solved it:

    http://www.redhat.com/archives/lvm-devel/2013-September/msg00036.html

Thanks,

	tglx
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