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Tue, 22 Sep 2026 00:44:46 -0700 (PDT) Date: Tue, 22 Sep 2026 09:44:44 +0200 From: Petr Mladek To: John Ogness Cc: Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko , Sebastian Andrzej Siewior , Jon Hunter , Thierry Reding , linux-kernel@vger.kernel.org, Ilpo =?iso-8859-1?Q?J=E4rvinen?= , Andy Shevchenko , Crescent Hsieh , Hugo Villeneuve , linux-serial@vger.kernel.org Subject: Re: [PATCH tty v2] serial: 8250: Change console_msr_work to IRQ_WORK_LAZY Message-ID: References: <20260921143939.170314-1-john.ogness@linutronix.de> Precedence: bulk X-Mailing-List: linux-serial@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: <20260921143939.170314-1-john.ogness@linutronix.de> On Mon 2026-09-21 16:45:36, John Ogness wrote: > Change console_msr_work (defers MSR handling) to be IRQ_WORK_LAZY, > thus not raising an IRQ upon irq_work queueing. The irq_work is then > handled on the next kernel tick. This additional delay is acceptable > because any pending MSR handling is also performed in the interrupt > handler, if mctrl is queried, and during console resume. Using > IRQ_WORK_LAZY has the benefit of not needing to raise an IRQ for > each line of atomic console printing when modem control is active. > > On a side note, the Tegra20 and Tegra30 platforms can hang if an > irq_work IRQ is raised while entering cpuidle states. This problem > was reproducible by performing atomic printing while entering cpuidle. > So this change also provides a workaround for these platforms (as > long as they are not running tickless). The discussion on this topic > is linked below. > > Link: https://lore.kernel.org/lkml/f3757a75-0ba1-4558-bf57-f19ab7e59a4c@nvidia.com > Fixes: d3539347022a ("serial: 8250: Switch to nbcon console, take 2") > Signed-off-by: John Ogness We did the same change also for the nbcon_irq_work which is used to wakeup printk kthreads in a safe context, see the commit 560f4deda32785e ("printk/nbcon: Change nbcon_irq_work to IRQ_WORK_LAZY"). Reviewed-by: Petr Mladek Best Regards, Petr