linux-kernel - Re: [PATCH] softirq: Provide a handshake for canceling tasklets via polling on PREEMPT

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Message-ID: <aJuYStGVBjyfVmZM@slm.duckdns.org>
Date: Tue, 12 Aug 2025 09:38:50 -1000
From: Tejun Heo <tj@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] softirq: Provide a handshake for canceling tasklets via
 polling on PREEMPT_RT

Hello,

On Tue, Aug 12, 2025 at 04:53:59PM +0200, Sebastian Andrzej Siewior wrote:
> Does the workqueue-BH code require the canceling from atomic context or
> was this just added because the API for BH and non-BH work items is the
> same and __cancel_work_sync() allows it?
> Could we avoid the busy-waiting for BH work items and rely on the
> wait_for_completion() below or do we need something similar to what I
> added here for the tasklet API?

The intention is to convert all BH users to workqueue-BH and remove BH
(that's what Linus wants and why workqueue-BH came to be), so the APIs
should be able to match up, I'm afraid. There were some attempts at pushing
the conversion but we've only made minimal progress. If you're looking at BH
users anyway and feel like it, please feel free to convert them.

Thanks.

-- 
tejun