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[2001:1c00:c1e:bf00:37a3:353b:be90:1238]) by smtp.gmail.com with ESMTPSA id v24sm44494772edw.23.2021.01.04.13.32.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Jan 2021 13:32:10 -0800 (PST) To: "Rafael J. Wysocki" Cc: ACPI Devel Maling List From: Hans de Goede Subject: Possible problem with "ACPI: scan: Defer enumeration of devices with _DEP lists" Message-ID: <7b32bd3a-4713-4283-df65-264ce035032e@redhat.com> Date: Mon, 4 Jan 2021 22:32:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Hi Rafael, To help with testing the "ACPI: scan: Defer enumeration of devices with _DEP lists" patch I've added it (the entire set) to my local 5.10 based tree about a month ago. Approx. 2 weeks ago I noticed that sometimes the kernel build from my local tree would not boot on a Lenovo Yoga Tablet 2 1051L machine. Reverting those changes fixed the problem that the device was sometimes not booting. When it did not boot, it would hang at: Starting udev Coldplug all Devices... And FWIW there was an oops about an unhandled kernel pagefault pointing to a sysfs directory entry reading function (I thought I saved the oops but it seems that I did not). I started debugging this but I did not really reach any conclusions before going on vacation. Fast forward to today when I build a 5.11-rc1 kernel and booted that 10 times on the Lenovo Yoga Tablet 2 1051L machine without issues... So this is really just a FYI, I'm pretty sure that I did not botch cherry-picking the patches on top of 5.10, do you know if there is a (somewhat) isolated patch which is necessary for the splitting of the scanning of the ACPI root into 2 steps which I might have missed ? Anyways this seems to be resolved, but I did have some ideas on how to pinpoint the culprit with the "backport" to 5.10, so if you get any bug-reports esp. ones about hanging at "Starting udev Coldplug all Devices..." I will get back to my 5.10 backport (I've a tag for it) and restart debugging on it. For now I'm happy to report that it is resolved with 5.11-rc1. Regards, Hans