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Date: Wed, 24 Jun 2026 11:33:29 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
	sched-ext@lists.linux.dev, netdev@vger.kernel.org,
	"David S . Miller" <davem@davemloft.net>,
	Andrea Righi <arighi@nvidia.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>, Ben Segall <bsegall@google.com>,
	Breno Leitao <leitao@debian.org>,
	Changwoo Min <changwoo@igalia.com>,
	David Vernet <void@manifault.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Eric Dumazet <edumazet@google.com>, Ingo Molnar <mingo@redhat.com>,
	Jakub Kicinski <kuba@kernel.org>,
	John Ogness <john.ogness@linutronix.de>,
	Juri Lelli <juri.lelli@redhat.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Paolo Abeni <pabeni@redhat.com>, Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	Simon Horman <horms@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>, Tejun Heo <tj@kernel.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Vlad Poenaru <vlad.wing@gmail.com>
Subject: Re: [PATCH 0/2] sched: Introduce and use deferred WARNs in sched
Message-ID: <20260624093329.GZ48970@noisy.programming.kicks-ass.net>
References: <20260623142650.265721-1-bigeasy@linutronix.de>
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In-Reply-To: <20260623142650.265721-1-bigeasy@linutronix.de>

On Tue, Jun 23, 2026 at 04:26:48PM +0200, Sebastian Andrzej Siewior wrote:
> This is a follow-up to the netconsole lockup reported
> 	https://lore.kernel.org/all/20260610183621.3915271-1-vlad.wing@gmail.com/
> 
> The idea is to use deferred printing for WARNs and use them in sched. I
> tried to use only where it looks that the rq lock acquired instead a
> plain s/WARN_ON/WARN_ON_DEFFERED which would be simpler.
> 
> This unholy deferred mess can be removed once we don't have legacy
> consoles anymore _or_ force force_legacy_kthread=true.

So I really don't see why we should do this. This has been a 'problem'
forever, and printk() is actually being fixed.