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SubjectRe: [PATCH 3/3] kernel/workqueue: Suppress a false positive lockdep complaint
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On Thu, 2018-10-25 at 19:02 +0200, Johannes Berg wrote:
> On Thu, 2018-10-25 at 15:05 +0000, Bart Van Assche wrote:
> > It can happen that the direct I/O queue creates and destroys an empty
> > workqueue from inside a work function.
>
> So, thinking about this more, can you guarantee (somehow) that the
> workqueue is empty at this point?

In general, no. But for the direct I/O case this can be guaranteed. Please
have a look at the code in sb_init_dio_done_wq() if you would not yet have
done this.

> Do you know how to reproduce this?

The lockdep complaint in the patch description is easy to reproduce. The
way I reproduce it is as follows:

git clone https://github.com/osandov/blktests
(cd blktests && ./check -q nvmeof-mp)

Bart.

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