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[83.28.44.212]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b79f4975b94sm67464566b.40.2025.12.04.00.22.56 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Thu, 04 Dec 2025 00:22:57 -0800 (PST) Date: Thu, 4 Dec 2025 09:23:59 +0100 From: Michal Pecio To: Forest Cc: Mathias Nyman , Greg Kroah-Hartman , Alan Stern , Heikki Krogerus , Stefan Eichenberger , Pawel Laszczak , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, regressions@lists.linux.dev Subject: Re: [REGRESSION][BISECTED] usb: hub: total system freeze after running adb Message-ID: <20251204092359.134635bd.michal.pecio@gmail.com> In-Reply-To: <3e4vhklrg4692n7hbh0pnrlhjkva68mk5v@sonic.net> References: <20251118105929.330f0042.michal.pecio@gmail.com> <3e4vhklrg4692n7hbh0pnrlhjkva68mk5v@sonic.net> Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 20 Nov 2025 14:18:00 -0800, Forest wrote: > On Tue, 18 Nov 2025 10:59:29 +0100, Michal Pecio wrote: > >How can you know nothing is logged if the machine becomes > >unresponsive? > > By watching the output of `stdbuf -o0 dmesg --follow` when it happens. > > Same results in a GUI terminal, a text console, and output redirected > to a `mount -o sync` non-journaled filesystem. I guess it's possible > that something *tried* to log a message, but if so, it didn't get > logged. This involves userspace, which stops working in cases like panic or full lockup of all CPUs. So you may be missing some final messages. If you have a PS/2 port, connect some keyboard and see if LEDs will start blinking - this means kernel panic. More reliable solution for getting logs from a broken system is serial console. Maybe netconsole would work too, I have never tried. And it seems it may also be possible to use xHCI debug capability (but it needs a special cable: A-to-A without Vbus). You could try CONFIG_DRM_PANIC, but it doesn't work on all GPUs yet and it will only help if it's a panic. Regards, Michal