From: Tejun Heo <tj@kernel.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Nigel Cunningham <nigel@nigelcunningham.com.au>,
"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 07:34:57 -0500 [thread overview]
Message-ID: <20131217123457.GD29989@htj.dyndns.org> (raw)
In-Reply-To: <8951916.gd5Uu6GpK1@vostro.rjw.lan>
Hello, Rafael.
On Tue, Dec 17, 2013 at 03:34:00AM +0100, Rafael J. Wysocki wrote:
> No, it isn't. [I guess it was originally, but it has not been the case
> for a very long time.] It is about getting user space interactions (all of
Heh... no wonder people are all so confused about this thing.
> the sysfs/ioctl/mmap/read/write/you-name-it thingies user space can do to
> devices) when we're calling device suspend/resume routines. The reason is
> that otherwise all of them would have had to do a "oh, are we suspending by
> the way?" check pretty much on every code path that can be triggered by
> user space.
Freezing userland is fine. I have no problem with that but up until
now the only use case that seems fundamentally valid to me is freezing
IO processing kthread in a driver as a cheap way to implement
suspend/resume. At this point, given the general level of confusion,
it seems to be costing more than benefiting.
> > Does that mean that it's safe to unfreeze before invoking resume?
>
> No, it isn't.
So, are you saying it's really about giving device drivers easy way to
implement suspend/resume? If that's the case, let's please make it
*way* more specific and clear - ie. things like helpers to implement
suspend/resume hooks trivially or whatnot. Freezable kthreads (and
now workqueues) have been becoming a giant mess for a while now.
Thanks.
--
tejun
next prev parent reply other threads:[~2013-12-17 12:35 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 [this message]
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
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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