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From: Tejun Heo <tj@kernel.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Jens Axboe <axboe@kernel.dk>,
	tomaz.solc@tablix.org, aaron.lu@intel.com,
	linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Fengguang Wu <fengguang.wu@intel.com>
Subject: Re: [PATCH] libata, freezer: avoid block device removal while system is frozen
Date: Tue, 17 Dec 2013 07:36:43 -0500	[thread overview]
Message-ID: <20131217123643.GE29989@htj.dyndns.org> (raw)
In-Reply-To: <2427190.pZk9AIZAjc@vostro.rjw.lan>

Hello, Rafael.

On Tue, Dec 17, 2013 at 03:38:05AM +0100, Rafael J. Wysocki wrote:
> On Friday, December 13, 2013 03:40:34 PM Tejun Heo wrote:
> > Hello,
> > 
> > So, this is the laughable workaround that I came up with.  Seriously,
> > this is tragic.  :(
> > 
> > Thanks.
> > 
> > ------- 8< -------
> > Freezable kthreads and workqueues are fundamentally problematic in
> > that they effectively introduce a big kernel lock widely used in the
> > kernel and have already been the culprit of several deadlock
> > scenarios.  This is the latest occurrence.
> 
> OK, so I'm too tired now to go through all that, but I'll look at it tomorrow.
> 
> The rule of thumb is to get rid of freezable kernel threads in the first
> place if possible anyway if they are causing problems to happen.

Yes, that'd be awesome.  In fact, getting rid of all kernel freezables
in non-low-level-drivers would be a great step forward.  That said, we
need something easily backportable so I think we probably need this
bandaid for immediate fix for now.

Thanks.

-- 
tejun

  reply	other threads:[~2013-12-17 12:36 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-13 17:49 Writeback threads and freezable Tejun Heo
2013-12-13 18:52 ` Tejun Heo
2013-12-13 20:40   ` [PATCH] libata, freezer: avoid block device removal while system is frozen Tejun Heo
2013-12-13 22:45     ` Nigel Cunningham
2013-12-13 23:07       ` Tejun Heo
2013-12-13 23:15         ` Nigel Cunningham
2013-12-14  1:55           ` Dave Chinner
2013-12-14 20:31           ` Tejun Heo
2013-12-14 20:36             ` Tejun Heo
2013-12-14 21:21               ` Nigel Cunningham
2013-12-17  2:35                 ` Rafael J. Wysocki
2013-12-17  2:34             ` Rafael J. Wysocki
2013-12-17 12:34               ` Tejun Heo
2013-12-18  0:35                 ` Rafael J. Wysocki
2013-12-18 11:17                   ` Tejun Heo
2013-12-18 21:48                     ` Rafael J. Wysocki
2013-12-18 21:39                       ` Tejun Heo
2013-12-18 21:41                         ` Tejun Heo
2013-12-18 22:04                           ` Rafael J. Wysocki
2013-12-19 23:35                             ` [PATCH wq/for-3.14 1/2] workqueue: update max_active clamping rules Tejun Heo
2013-12-20  1:26                               ` Rafael J. Wysocki
2013-12-19 23:37                             ` [PATCH wq/for-3.14 2/2] workqueue: implement @drain for workqueue_set_max_active() Tejun Heo
2013-12-20  1:31                               ` Rafael J. Wysocki
2013-12-20 13:32                                 ` Tejun Heo
2013-12-20 13:56                                   ` Rafael J. Wysocki
2013-12-20 14:23                                     ` Tejun Heo
2013-12-16 12:12         ` [PATCH] libata, freezer: avoid block device removal while system is frozen Ming Lei
2013-12-16 12:45           ` Tejun Heo
2013-12-16 13:24             ` Ming Lei
2013-12-16 16:05               ` Tejun Heo
2013-12-17  2:38     ` Rafael J. Wysocki
2013-12-17 12:36       ` Tejun Heo [this message]
2013-12-18  0:23         ` Rafael J. Wysocki
2013-12-17 12:50     ` [PATCH v2] " Tejun Heo
2013-12-18  1:04       ` Rafael J. Wysocki
2013-12-18 11:08         ` Tejun Heo
2013-12-18 12:07       ` [PATCH v3] " Tejun Heo
2013-12-18 22:08         ` Rafael J. Wysocki
2013-12-19 17:24           ` Tejun Heo
2013-12-19 18:54         ` [PATCH v4] " Tejun Heo
2013-12-14  1:53 ` Writeback threads and freezable Dave Chinner
2013-12-14 17:30   ` Greg Kroah-Hartman
2013-12-14 20:23   ` Tejun Heo
2013-12-16  3:56     ` Dave Chinner
2013-12-16 12:51       ` Tejun Heo
2013-12-16 12:56         ` Tejun Heo
2013-12-18  0:35           ` Dave Chinner
2013-12-18 11:43             ` Tejun Heo
2013-12-18 22:14               ` Rafael J. Wysocki
2013-12-19  4:08               ` Dave Chinner
2013-12-19 16:24                 ` Tejun Heo
2013-12-20  0:51                   ` Dave Chinner
2013-12-20 14:51                     ` Tejun Heo
2013-12-20 14:00                   ` Rafael J. Wysocki

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