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SubjectRe: [PATCH v3 0/6] usb: hub: convert khubd into workqueue
On Fri, 19 Sep 2014, Petr Mladek wrote:

> The 3rd version of the patchset is slightly reordered and refactored
> as suggested earlier. See below for more details.
>
> IMHO, the result is more clean. But feel free to ask me to revert it.
> I do not want to make the review more complicated. Well, I double checked
> the diff of patches files between v2 and v3. It is pretty small and only
> the expected changes are there.
>
> Changes in:
> + v3:
> + split the optimization of hub->hdev reference counting
> into separate patch; usable standalone (1st patch)
>
> + switch order of the two patches that convert the kthread
> and that remove the while cycle in hub_event(); it is
> cleaner (2nd and 3rd patch)
>
> + use ordered workqueue by default; it makes it compatible
> with the original kthread solution (3rd patch)
>
> + added optional patch that allows to process events
> in parallel (6th patch)
>
> + fixed the suggested stylistic problems (2nd and 3rd patch)
>
>
> + v2:
> + solved potential races:
> + get hub->kref in kick_hub_wq()
> + call usb_get_dev(hdev) in hub_probe()
> and usb_put_dev(hdev) in hub_release()
> + INIT_WORK only once in hub_probe()
>
> + do not call cancel_work_sync() in hub_disconnect()
> to keep it fast
>
> + rename kick_khubd() to kick_hub_wq() already
> in the first patch; IMHO, it is cleaner while
> adding only very few changes
>
>
> The workqueue API is well defined and tested. It has many options
> that could be used to tune the scheduling. The code is usually
> easier and thus more safe. It allows to avoid the extra thread
> in most cases. It has has clearly defined behavior vrt. system suspend.
>
> This patchset converts khubd into the workqueue. It saves one thread,
> lock, and list.
>
> It looks huge but the main change is in the first patch. The rest is
> simple renaming of functions, comments and documentation.
>
>
> Thanks a lot Alan Stern and Tejun Heo for hints and guidance.
>
> The patches can be applied either against Linus' tree or linux-next.

Very nice work. I haven't tried it out, but it all looks good. No
doubt we will be able to sort out unforeseen troubles if any arise,
without much difficulty.

For all six patches,

Acked-by: Alan Stern <stern@rowland.harvard.edu>

Alan Stern



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