Re: [PATCHSET wq/for-6.9,6.10] workqueue: Implement disable/enable_work()

[Allen]

Tejun,
>
> Sorry about the late reply.
>

No worries :)

> On Thu, Feb 22, 2024 at 12:26:35PM -0800, Allen wrote:
> >  I do understand the work bits, but I don't fully understand the
> > concept of colors
> > (work_color, flush_color). A swift overview of it would be highly appreciated.
>
> That's just to group work items for flush_workqueue(). Let's say there are
> work items which are queued in sequence, 1 to 8. Let's also say that there
> are three flush_workqueue() attempts which take place after work item 2, 4
> and 6. Then, the flush colors A, B, C, D are assigned so that:
>
>   work items        1     2     3     4     5     6     7     8
>   flush_workqueue            ^           ^           ^
>                     \-----/     \-----/     \-----/     \------~~~
>   flush_color          A           B           C            D
>
> and the flush_workqueue() code waits for its preceding colors to be drained
> to implement flushing.
>
> It's just a way to keep track of the number of work items in flight which
> were issued before a certain point in time. It's expensive to do that for
> arbitrary number of points in time, so it just has N slots for groups and
> calls them flush colors.
>

 Thank you very much. This is very helpful.

- Allen

> This shouldn't really matter for the bh conversion given that everyone
> operates on individual work item.
>
> Thanks.
>
> --
> tejun