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Fri, 28 Aug 2026 03:25:40 -0700 (PDT) Date: Fri, 28 Aug 2026 12:25:38 +0200 From: Petr Mladek To: John Ogness Cc: Sergey Senozhatsky , Steven Rostedt , Sebastian Andrzej Siewior , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH printk] printk/nbcon: Change nbcon_irq_work to IRQ_WORK_LAZY Message-ID: References: <20260827184750.203521-1-john.ogness@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260827184750.203521-1-john.ogness@linutronix.de> On Thu 2026-08-27 20:53:38, John Ogness wrote: > For some platforms it is a problem to queue irq_work when entering > cpuidle states. Since nbcon uses irq_work for waking the printing > kthreads, any printk() calls when entering cpuidle states can lead > to the affected hardware hanging. Tegra20 and Tegra30 are examples > of such platforms. Avoiding raising the irq_work IRQ has shown to > circumvent the problem. > > Change the nbcon_irq_work to be IRQ_WORK_LAZY, thus not raising > an IRQ upon irq_work queuing. The irq_work is then handled on the > next interrupt (worst case, kernel tick). This additional delay is > acceptable because nbcon_irq_work is only responsible for > non-emergency deferred printing, which is delayed anyway. This also > has the benefit of not needing to raise an IRQ for each printk() > call. > > Link: https://lore.kernel.org/lkml/f3757a75-0ba1-4558-bf57-f19ab7e59a4c@nvidia.com > Fixes: 76f258bf3f2a ("printk: nbcon: Introduce printer kthreads") > Signed-off-by: John Ogness Looks good to me: Reviewed-by: Petr Mladek I am going to wait for v2 which would fix the preexisting problem reported by Sashiko. Anyway, I am going to queue this for 7.3-rcX to prevent regressions caused by converting the uart 8250 console driver into nbcon API. Best Regards, Petr