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

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Message-ID: <aK3gbywOkrksPQeV@slm.duckdns.org>
Date: Tue, 26 Aug 2025 06:27:27 -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 26, 2025 at 05:49:42PM +0200, Sebastian Andrzej Siewior wrote:
> On 2025-08-22 08:07:47 [-1000], Tejun Heo wrote:
> > Hello, Sebastian.
> Hi Tejun,
> 
> > Agreed, once we get rid of them, we can drop the whole block for both RT and
> > !RT - ie. revert the patch that added it. But, wouldn't it be more orderly
> > to match the semantics in both cases even if the behavior isn't quite
> > optimal? We can put some comment noting what to do once the culprits are
> > updated to not need it.
> 
> Sure. I am only worried that if something is possible, people will use
> it. I don't think things will change if we debate for another week ;)
> The first patch here in this thread should provide the symmetrical API.
> 
> Oh. We could also hide this polling API behind a special API which is
> hidden just for three special cases so everyone else would do the right
> job.

Oh yeah, that makes a lot of sense to me - splitting it out into something
which is named explicitly to discourage further usages.

Thanks.

-- 
tejun