netdev - Re: [PATCH 9/9] mmc: Convert from tasklet to BH workqueue

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Message-ID: <ZgWZDtNU4tCwqyeu@slm.duckdns.org>
Date: Thu, 28 Mar 2024 06:21:34 -1000
From: Tejun Heo <tj@...nel.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
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Subject: Re: [PATCH 9/9] mmc: Convert from tasklet to BH workqueue

Hello,

On Thu, Mar 28, 2024 at 01:53:25PM +0100, Ulf Hansson wrote:
> At this point we have suggested to drivers to switch to use threaded
> irq handlers (and regular work queues if needed too). That said,
> what's the benefit of using the BH work queue?

BH workqueues should behave about the same as tasklets which have more
limited interface and is subtly broken in an expensive-to-fix way (around
freeing in-flight work item), so the plan is to replace tasklets with BH
workqueues and remove tasklets from the kernel.

The [dis]advantages of BH workqueues over threaded IRQs or regular threaded
workqueues are the same as when you compare them to tasklets. No thread
switching overhead, so latencies will be a bit tighter. Wheteher that
actually matters really depends on the use case. Here, the biggest advantage
is that it's mostly interchangeable with tasklets and can thus be swapped
easily.

Thanks.

-- 
tejun