Subject: Re: Softirq priority inversion from "softirq: reduce latencies"

From: Mike Galbraith <[email-masked]>
Date: Sun, 28 Feb 2016 06:55:57 +0100

On Sat, 2016-02-27 at 10:19 -0800, Peter Hurley wrote:
> Hi Eric,
> 
> For a while now, we've been struggling to understand why we've been
> observing missed uart rx DMA.
> 
> Because both the uart driver (omap8250) and the dmaengine driver
> (edma) were (relatively) new, we assumed there was some race between
> starting a new rx DMA and processing the previous one.

Hrm, relatively new + tasklet woes rings a bell.  Ah, that..

<quote>
What's worse is that at the point where this code was written it was
already well known that tasklets are a steaming pile of crap and
should die.
</quote>

Source thereof https://lwn.net/Articles/588457/

	-Mike