linux-kernel - [PATCH] PM / EM: postpone creating the debugfs dir till fs

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Message-Id: <20210323145608.29832-1-lukasz.luba@arm.com>
Date:   Tue, 23 Mar 2021 14:56:08 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        rjw@...ysocki.net, rafael@...nel.org
Cc:     ionela.voinescu@....com, Dietmar.Eggemann@....com,
        lukasz.luba@....com, gregkh@...uxfoundation.org
Subject: [PATCH] PM / EM: postpone creating the debugfs dir till fs_initcall

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@....com>
Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
Hi Rafael,

Please take this patch into your PM v5.12 fixes. The change described in
the patch above landed in v5.12-rc1. Some of our EAS/EM tests are failing.

Regards,
Lukasz

 kernel/power/energy_model.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index 1358fa4abfa8..0f4530b3a8cd 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -98,7 +98,7 @@ 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 device *dev) {}
 static void em_debug_remove_pd(struct device *dev) {}
-- 
2.17.1