[dm-devel] workqueues and percpu (was: [PATCH] dm: remake of the verity target)
Tejun Heo
tj at kernel.org
Fri Mar 9 21:20:49 UTC 2012
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
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