From: Andi Kleen <andi@firstfloor.org>
To: Radoslaw Szkodzinski <lkml@astralstorm.puszkin.org>
Cc: Andi Kleen <andi@firstfloor.org>,
Arjan van de Ven <arjan@infradead.org>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks
Date: Mon, 3 Dec 2007 11:27:15 +0100 [thread overview]
Message-ID: <20071203102715.GC28560@one.firstfloor.org> (raw)
In-Reply-To: <20071203111520.33ed2139@astralstorm.puszkin.org>
> Kernel waiting 2 minutes on TASK_UNINTERRUPTIBLE is certainly broken.
What should it do when the NFS server doesn't answer anymore or
when the network to the SAN RAID array located a few hundred KM away develops
some hickup? Or just the SCSI driver decides to do lengthy error
recovery -- you could argue that is broken if it takes longer
than 2 minutes, but in practice these things are hard to test
and to fix.
> Yes, that's exactly why the patch is needed - to find the bugs and fix
The way to find that would be to use source auditing, not break
perfectly fine error handling paths. Especially since this at least
traditionally hasn't been considered a bug, but a fundamental design
parameter of network/block/etc. file systems
> CIFS and similar have to be fixed - it tends to lock the app
> using it, in unkillable state.
Actually that's not true. You can umount -f and then kill for at least
NFS and CIFS. Not sure it is true for the other network file systems
though.
You could in theory do TASK_KILLABLE for all block devices too (not
a bad thing; I would love to have it).
But it would be equivalent in work (has to patch all the same places with
similar code) to Suparna's big old fs AIO retry
patchkit that never went forward because everyone was too worried
about excessive code impact. Maybe that has changed, maybe not ...
And even then you would need to check all possible error handling
paths (scsi_error and low level drivers at least) that they all
finish in less than two minutes.
> > > wild guesses. Only one way to get the real false positive percentage.
> >
> > Yes let's break things first instead of looking at the implications closely.
>
> Throwing _rare_ stack traces is not breakage. 120s task_uninterruptible
Sorry that's total bogus. Throwing a stack trace is the kernel
equivalent of sending S.O.S. and worrying the user significantly,
taxing reporting resources etc. and in the interest of saving
everybody trouble it should only do that when it is really
sure it is truly broken.
> in the usual case (no errors) is already broken - there are no sane
> loads that can invoke that IMO.
You are wrong on that.
-Andi
next prev parent reply other threads:[~2007-12-03 10:27 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-01 9:20 [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks Ingo Molnar
2007-12-01 18:31 ` David Rientjes
2007-12-01 18:33 ` Ingo Molnar
2007-12-01 18:42 ` David Rientjes
2007-12-01 19:36 ` Ingo Molnar
2007-12-02 0:54 ` Ingo Oeser
2007-12-02 8:58 ` Ingo Molnar
2007-12-02 15:52 ` David Rientjes
2007-12-02 18:57 ` Andi Kleen
2007-12-02 18:59 ` Ingo Molnar
2007-12-02 19:41 ` Arjan van de Ven
2007-12-02 20:08 ` Ingo Molnar
2007-12-02 20:09 ` Andi Kleen
2007-12-02 20:26 ` Ingo Molnar
2007-12-02 20:47 ` Andi Kleen
2007-12-02 21:10 ` Ingo Molnar
2007-12-02 21:19 ` Andi Kleen
2007-12-02 21:24 ` Ingo Molnar
2007-12-02 21:34 ` Andi Kleen
2007-12-02 22:25 ` Ingo Molnar
2007-12-02 22:18 ` Arjan van de Ven
2007-12-02 22:20 ` Ingo Molnar
2007-12-03 0:00 ` Andi Kleen
2007-12-02 22:43 ` Arjan van de Ven
2007-12-03 0:07 ` Andi Kleen
2007-12-03 0:59 ` Arjan van de Ven
2007-12-03 9:55 ` Andi Kleen
2007-12-03 10:15 ` Radoslaw Szkodzinski
2007-12-03 10:23 ` Ingo Molnar
2007-12-03 10:27 ` Andi Kleen [this message]
2007-12-03 10:38 ` Ingo Molnar
2007-12-03 11:04 ` Andi Kleen
2007-12-03 11:59 ` Ingo Molnar
2007-12-03 12:13 ` Andi Kleen
2007-12-03 12:28 ` Ingo Molnar
2007-12-03 12:41 ` Andi Kleen
2007-12-03 13:00 ` Ingo Molnar
2007-12-03 13:14 ` Andi Kleen
[not found] ` <20071203132955.GA31354@elte.hu>
2007-12-03 13:41 ` Radoslaw Szkodzinski
2007-12-03 13:59 ` Ingo Molnar
2007-12-03 14:15 ` Andi Kleen
2007-12-03 13:48 ` Andi Kleen
2007-12-03 13:55 ` Ingo Molnar
2007-12-03 14:17 ` Andi Kleen
2007-12-03 14:33 ` Ingo Molnar
2007-12-03 17:02 ` Ray Lee
2007-12-03 13:50 ` Pekka Enberg
2007-12-03 13:57 ` Ingo Molnar
2007-12-03 14:14 ` Andi Kleen
2007-12-03 14:19 ` Ingo Molnar
2007-12-03 17:57 ` Andrew Morton
2007-12-03 18:28 ` Rafael J. Wysocki
2007-12-03 19:24 ` Ingo Molnar
2007-12-03 22:47 ` Rafael J. Wysocki
2007-12-04 0:05 ` Ingo Molnar
2007-12-03 15:23 ` Arjan van de Ven
2007-12-03 16:36 ` Andi Kleen
2007-12-05 22:31 ` Mark Lord
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