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Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Breno Leitao , Clark Williams , Steven Rostedt , linux-rt-devel@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Frederic Weisbecker , Ingo Molnar , Vincent Guittot , Dietmar Eggemann , K Prateek Nayak Subject: Re: [PATCH net] netpoll: run NAPI poll in softirq context to avoid rq->lock self-deadlock Message-ID: References: <20260610183621.3915271-1-vlad.wing@gmail.com> <20260611191114.5bc43a59@kernel.org> <20260616103529.Yh9Dxsjp@linutronix.de> <20260616081128.04e2c8dd@kernel.org> <20260616153122.keHMKvVT@linutronix.de> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260616153122.keHMKvVT@linutronix.de> On Tue 2026-06-16 17:31:22, Sebastian Andrzej Siewior wrote: > On 2026-06-16 08:11:28 [-0700], Jakub Kicinski wrote: > > > > > > Adding sched and printk folks for opinions while eyeballing > > > WARN_ON_DEFERRED(). > > > > Thanks a lot for looking into this! To be clear - the printk_deferred / > > WARN_DEFERRED would be just for stable? Or there's still some > > sensitivity even with nbcon? > > We already have printk_deferred(). WARN_DEFERRED() would be new. I > *think* this is not limited netpoll/ netconsole but all console drivers > not using CON_NBCON if the printk (via WARN) occurs with the rq held. > I don't remember all the details but printk_deferred() was introduced to > circumvent this until printk is fixed. Just to make it clear. The problem with the legacy consoles is that they are called under console_lock() which is a semaphore. And it calls wake_up_process() in console_unlock() when there is another waiter on the lock. > Once we get rid of those legacy drivers and NBCON is the default we can > get rid of printk_deferred() :) Yup. Best Regards, Petr