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Date: Wed, 25 Mar 2026 15:03:24 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Qiliang Yuan <realwujing@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
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	linux-kernel@vger.kernel.org, rcu@vger.kernel.org,
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Subject: Re: [PATCH 07/15] watchdog: Allow runtime toggle of lockup detector
 affinity
Message-ID: <20260325140324.GD3738786@noisy.programming.kicks-ass.net>
References: <20260325-dhei-v12-final-v1-0-919cca23cadf@gmail.com>
 <20260325-dhei-v12-final-v1-7-919cca23cadf@gmail.com>
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In-Reply-To: <20260325-dhei-v12-final-v1-7-919cca23cadf@gmail.com>

On Wed, Mar 25, 2026 at 05:09:38PM +0800, Qiliang Yuan wrote:
> The hardlockup detector threads are affined to CPUs based on the
> HK_TYPE_TIMER housekeeping mask at boot. If this mask is updated at
> runtime, these threads remain on their original CPUs, potentially
> running on isolated cores.
> 
> Synchronize watchdog thread affinity with HK_TYPE_TIMER updates.

Doesn't the normal watchdog run off of perf, using NMIs? How is that
TIMER?

And again, why do you think you need more than _ONE_ mask?

In the end, NOHZ_FULL needs all the masks to be the same anyway. There
is absolutely no sane reason to have this much configuration space.