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[210.128.90.14]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-747afed4399sm8963618b3a.77.2025.06.03.02.03.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Jun 2025 02:03:19 -0700 (PDT) From: Ryo Takakura To: mhklinux@outlook.com Cc: fj6611ie@aa.jp.fujitsu.com, gregkh@linuxfoundation.org, jirislaby@kernel.org, john.ogness@linutronix.de, pmladek@suse.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux@armlinux.org.uk Subject: Re: Problem with nbcon console and amba-pl011 serial port Date: Tue, 3 Jun 2025 18:03:13 +0900 Message-Id: <20250603090313.126850-1-ryotkkr98@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi! On Tue, 3 Jun 2025 03:18:23 +0000, Michael Kelley wrote: >The problem is timing dependent. In some cases, the "pr/ttyAMA0" >thread is evidently able to get the message out before panic() calls >pr_emerg(). In my case running as a guest on Hyper-V, the pl011 device >in the guest VM is emulated by Hyper-V. Each pl011 register access >traps to the hypervisor, which slows things down and probably makes >the problem more likely. But from what I can see, the underlying >race condition exists regardless. I believe the issue is not amba-pl011 specific, so maybe John and Petr better be Cced as well. Sincerely, Ryo Takakura