This is a note to let you know that I've just added the patch titled PM: EM: postpone creating the debugfs dir till fs_initcall to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pm-em-postpone-creating-the-debugfs-dir-till-fs_init.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 4719a1e186a52bcfcfd6915b1144056ab3a4c8a5 Author: Lukasz Luba <lukasz.luba@xxxxxxx> Date: Tue Mar 23 14:56:08 2021 +0000 PM: EM: postpone creating the debugfs dir till fs_initcall [ Upstream commit fb9d62b27ab1e07d625591549c314b7d406d21df ] The debugfs directory '/sys/kernel/debug/energy_model' is needed before the Energy Model registration can happen. With the recent change in debugfs subsystem it's not allowed to create this directory at early stage (core_initcall). Thus creating this directory would fail. Postpone the creation of the EM debug dir to later stage: fs_initcall. It should be safe since all clients: CPUFreq drivers, Devfreq drivers will be initialized in later stages. The custom debug log below prints the time of creation the EM debug dir at fs_initcall and successful registration of EMs at later stages. [ 1.505717] energy_model: creating rootdir [ 3.698307] cpu cpu0: EM: created perf domain [ 3.709022] cpu cpu1: EM: created perf domain Fixes: 56348560d495 ("debugfs: do not attempt to create a new file before the filesystem is initalized") Reported-by: Ionela Voinescu <ionela.voinescu@xxxxxxx> Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx> Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c index 0a9326f5f421..8dac32bd9089 100644 --- a/kernel/power/energy_model.c +++ b/kernel/power/energy_model.c @@ -74,7 +74,7 @@ static int __init em_debug_init(void) return 0; } -core_initcall(em_debug_init); +fs_initcall(em_debug_init); #else /* CONFIG_DEBUG_FS */ static void em_debug_create_pd(struct em_perf_domain *pd, int cpu) {} #endif