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From: Tejun Heo <tj@kernel.org>
To: Mandeep Singh Baines <msb@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Mikulas Patocka <mpatocka@redhat.com>,
	linux-kernel@vger.kernel.org, dm-devel@redhat.com,
	Alasdair G Kergon <agk@redhat.com>,
	Will Drewry <wad@chromium.org>,
	Elly Jones <ellyjones@chromium.org>,
	Milan Broz <mbroz@redhat.com>,
	Olof Johansson <olofj@chromium.org>,
	Steffen Klassert <steffen.klassert@secunet.com>,
	Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: workqueues and percpu (was: [PATCH] dm: remake of the verity target)
Date: Fri, 9 Mar 2012 13:20:49 -0800	[thread overview]
Message-ID: <20120309212049.GD24890@google.com> (raw)
In-Reply-To: <20120309211512.GL27051@google.com>

Hello,

On Fri, Mar 09, 2012 at 01:15:12PM -0800, Mandeep Singh Baines wrote:
> In this case, I need the per-cpu data for the duration of calculating
> a cryptographics hash on a 4K page of data. That's a long time to disable
> pre-emption.

How long are we talking about?  Tens of microsecs, tens of millisecs?

> I could fix the bug temporarily by adding get/put for the per_cpu data
> but would that be acceptable? I'm not sure what the OK limit is for how
> long one can disable preemption. An alternative fix would be not allow
> CONFIG_VERITY when CONFIG_HOTPLUG_CPU. Once workqueues are fixed, I could
> remove that restriction.

I think the right thing to do for now is to add cpu hotplug notifier
and do flush_work_sync() on the work item.  We can later move that
logic into workqueue and remove it from crypto.

Thanks.

-- 
tejun

  reply	other threads:[~2012-03-09 21:20 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-02  0:33 [PATCH] dm: verity target Mandeep Singh Baines
2012-03-02 16:08 ` Mandeep Singh Baines
2012-03-02 16:08   ` Mandeep Singh Baines
2012-03-04 19:18 ` [PATCH] dm: remake of the " Mikulas Patocka
2012-03-04 19:35   ` userspace hashing utility for dm-verity Mikulas Patocka
2012-03-06 21:59   ` [PATCH] dm: remake of the verity target Mandeep Singh Baines
2012-03-08 22:21     ` workqueues and percpu (was: [PATCH] dm: remake of the verity target) Mikulas Patocka
2012-03-08 22:39       ` Andrew Morton
2012-03-08 23:15         ` Tejun Heo
2012-03-08 23:30           ` Andrew Morton
2012-03-09  0:33             ` Tejun Heo
2012-03-09  0:51               ` Tejun Heo
2012-03-09 21:15           ` Mandeep Singh Baines
2012-03-09 21:20             ` Tejun Heo [this message]
2012-03-09 22:06               ` Mandeep Singh Baines
2012-08-14 17:54                 ` Tejun Heo
2012-08-14 17:54                   ` Tejun Heo
2012-03-13 22:20     ` [PATCH] dm: remake of the verity target Mikulas Patocka
2012-03-14 21:13       ` Will Drewry
2012-03-17  1:16         ` Mikulas Patocka
2012-03-17  3:06           ` Will Drewry
2012-03-14 21:43       ` Mandeep Singh Baines
2012-03-20 15:41       ` Mandeep Singh Baines
2012-03-21  0:54         ` Mikulas Patocka
2012-03-21  3:03           ` Mandeep Singh Baines
2012-03-21  3:11           ` [dm-devel] " Mikulas Patocka
2012-03-21  3:30             ` Mandeep Singh Baines
2012-03-21  3:44               ` Mikulas Patocka
2012-03-21  3:49                 ` Mandeep Singh Baines
2012-03-21 17:08                   ` Mikulas Patocka
2012-03-21 17:08                     ` [dm-devel] " Mikulas Patocka
2012-03-21 17:09                     ` Mikulas Patocka
2012-03-21 17:09                       ` [dm-devel] " Mikulas Patocka
2012-03-22 17:41                     ` Mandeep Singh Baines
2012-03-22 21:52                       ` Mikulas Patocka
2012-03-23  3:15                         ` Mandeep Singh Baines
2012-03-24  3:48                           ` Mikulas Patocka
2012-03-21  1:10         ` Mikulas Patocka

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