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authorHans de Goede <hdegoede@redhat.com>2021-01-25 22:09:09 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2021-01-27 20:48:12 +0300
commit041142d7d25294c17d39552ae51c1d8d89434010 (patch)
treee834236ddb32e7f84ba2b64061493a761c63eff0 /drivers/acpi
parent84f9017c37c479c4f70456a645d24d2296ad2208 (diff)
downloadlinux-041142d7d25294c17d39552ae51c1d8d89434010.tar.xz
ACPI: platform-profile: Fix possible deadlock in platform_profile_remove()
After a rmmod thinkpad_acpi, lockdep pointed out this possible deadlock: Our _show and _store sysfs attr functions get called with the kn->active lock held for the sysfs attr and then take the profile_lock. sysfs_remove_group() also takes the kn->active lock for the sysfs attr, so if we call it with the profile_lock held, then we get an ABBA deadlock. platform_profile_remove() must only be called by drivers which have first *successfully* called platform_profile_register(). Anything else is a driver bug. So the check for cur_profile being set before calling sysfs_remove_group() is not necessary and it can be dropped. It is safe to call sysfs_remove_group() without holding the profile_lock since the attr-group group cannot be re-added until after we clear cur_profile. Change platform_profile_remove() to only hold the profile_lock while clearing the cur_profile, fixing the deadlock. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi')
-rw-r--r--drivers/acpi/platform_profile.c8
1 files changed, 2 insertions, 6 deletions
diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
index 80e9df427eb8..4a59c5993bde 100644
--- a/drivers/acpi/platform_profile.c
+++ b/drivers/acpi/platform_profile.c
@@ -164,13 +164,9 @@ EXPORT_SYMBOL_GPL(platform_profile_register);
int platform_profile_remove(void)
{
- mutex_lock(&profile_lock);
- if (!cur_profile) {
- mutex_unlock(&profile_lock);
- return -ENODEV;
- }
-
sysfs_remove_group(acpi_kobj, &platform_profile_group);
+
+ mutex_lock(&profile_lock);
cur_profile = NULL;
mutex_unlock(&profile_lock);
return 0;