[PATCH v4 0/3] ACPI: battery: Do not generate too much pressure on ACPI methods

[PATCH v4 0/3] ACPI: battery: Do not generate too much pressure on ACPI methods

[Rong Zhang]

The acpi_battery_notify() and acpi_battery_get_property() callbacks
sometimes generate too much pressure on corresponding ACPI methods. On
some devices with fragile ACPI implementation, these methods share the
same mutex protecting EC accesses (hence slow to execute) with a lot of
other EC-related methods. Such pressure on them eventually leads to a
catastrophic situation that a bunch of ACPI method calls fail to acquire
the same mutex due to timeout. The firmware of these devices doesn't
handle mutex acquisition failure gracefully and return garbage data,
causing even more chaos.

For acpi_battery_notify(), a very common pattern in EC queries that
emits two consecutive battery notifications with event IDs 0x80 and 0x81
updates battery state and calls power_supply_changed() twice within a
short period, generating significant pressure on _STA, _BST and
_BIX/_BIF methods. Not only that, power_supply_ext properties may also
rely on some other ACPI methods, so both uevent assembling and userspace
processes call them. It becomes a nightmare when all these methods share
the same ACPI mutex and hence vulnerable to lock starvation. Even worse,
after the first uevent reaches userspace, some userspace processes start
to read all battery properties in order to refresh their internal
states, which competes with the second notification's handling and
uevent assembling, exacerbating the lock starvation.

For acpi_battery_get_property(), it generates too much pressure on the
_BST method because of the lack of synchronization. In detail, it
sometimes nullifies the cache mechanism of acpi_battery_get_state() when
multiple processes read power supply properties simultaneously, which
usually happens after a uevent. Normally, emitting a uevent implies that
the cache must have been refreshed due to power_supply_uevent() reading
all properties, so the mentioned processes should have seen cache hits.
Unfortunately, these fragile devices' power_supply_ext properties are
somehow slow to read after battery events, resulting in cache expiration
before power_supply_uevent() finishes. Hence, once the uevent reaches
userspace, the _BST method will be executed multiple times within a
short period due to userspace processes reading all properties again.

Improve acpi_battery_notify() by merging at most 16 consecutive battery
notifications within 10ms using a delayed work, so that they only
refresh and/or update battery state once. ACPI netlink event and
notifier call chain are still triggered multiple times in order not to
break other components. Finally, call power_supply_changed() once and
lead to a single uevent instead of a bunch, preventing userspace
programs from causing too much pressure on power supply properties and
the underlying ACPI methods.

Fix acpi_battery_get_property() by introducing a mutex to protect all
accesses to battery properties, so that acpi_battery_get_property() can
take the advantage of the mutex and synchronize itself. This also
prevents potential race conditions, e.g., when multiple tasks read power
supply properties simultaneously, or when other callbacks are called
during its execution.

Since the series touches acpi_battery_alarm_store(), also convert the
use of sscanf("%lu\n") into the more preferred kstrtoul() beforehand.

With the series, the lock starvation issue on mentioned devices is
greatly improved according to the feedback from one of the device
owners.

Tested-by: Avraham Hollander <anhollander516@gmail.com>
Reported-by: Rick <rickk1166@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221065
Signed-off-by: Rong Zhang <i@rong.moe>

---
Changes in v4:
- Rebase and adopt devres-based resource management
- Refactor acpi_battery_notify() to hold the mutex across the entire
  function to improve readability and drop unnecessary variables (thanks
  Rafael J. Wysocki)
- Link to v3: https://patch.msgid.link/20260611-b4-acpi-battery-notification-v3-0-f9390382c5a4@rong.moe

Changes in v3:
- Address Sashiko's concerns on my last-minute changes:
  - Set the number base to 10 in order not to break the ABI
  - Do not overwrite the initial value of `ret' in
    acpi_battery_get_property()
  - https://sashiko.dev/#/patchset/20260611-b4-acpi-battery-notification-v2-0-4e8ed651a151%40rong.moe
- Link to v2: https://patch.msgid.link/20260611-b4-acpi-battery-notification-v2-0-4e8ed651a151@rong.moe

Changes in v2:
- Address Sashiko's concerns:
  - Return from acpi_battery_notification_worker() early when the fifo
    is empty
  - Use pr_err_ratelimited() for potential event storms
  - Add missing `\n' in a printk message
  - Use a separated mutex to protect all properties instead of reusing
    update_lock
  - https://sashiko.dev/#/patchset/20260527-b4-acpi-battery-notification-v1-0-2303bed8ec0b%40rong.moe
- Minimalize the critical section of acpi_battery_notify()
- Rearrange the series
- Dropped Tested-by from patch 3 due to massive rewrite
- Link to v1: https://patch.msgid.link/20260527-b4-acpi-battery-notification-v1-0-2303bed8ec0b@rong.moe

---
Rong Zhang (3):
      ACPI: battery: Merge consecutive battery notifications
      ACPI: battery: Use kstrtoul() over sscanf("%lu\n")
      ACPI: battery: Protect all properties with a separated mutex

 drivers/acpi/battery.c | 244 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 187 insertions(+), 57 deletions(-)
---
base-commit: 94515f3a7d4256a5062176b7d6ed0471938cd51a
change-id: 20260520-b4-acpi-battery-notification-90d781a3f217

Thanks,
Rong

[PATCH v4 1/3] ACPI: battery: Merge consecutive battery notifications

[Rong Zhang]

It's a very common pattern to emit consecutive battery notifications,
for example:

    Method (_Qxx, 0, NotSerialized)
    {
        Notify (BAT0, 0x80) // Status Change
        Notify (BAT0, 0x81) // Information Change
    }

In this case, the current code path will update battery state twice
within a short period, which is not optimal, as the same data are
fetched twice. Moreover, both notifications are likely to call
power_supply_changed(), causing power_supply_uevent() to read all
battery properties in order to assemble uevents. Even worse, after the
first uevent reaches userspace, some userspace processes start to read
all battery properties in order to refresh their internal states, which
competes with the second notification's handling and uevent assembling.

This generates significant pressure on _STA, _BST and _BIX/_BIF methods.
Not only that, power_supply_ext properties may also rely on some other
ACPI methods, so both uevent assembling and userspace processes call
them. It becomes a nightmare when all these methods share the same ACPI
mutex protecting EC accesses and hence vulnerable to lock starvation.
This is exactly the case of some Lenovo devices, where the mentioned EC
query pattern eventually leads to a catastrophic situation that a bunch
of ACPI methods (including but not limited to the mentioned ones) fail
to acquire the same mutex due to timeout. These devices don't handle
mutex acquisition failure gracefully and return garbage data, causing
even more chaos.

Improve battery notification handling by merging at most 16 consecutive
battery notifications within 10ms using a delayed work, so that they
only refresh and/or update battery state once. ACPI netlink event and
notifier call chain are still triggered multiple times in order not to
break other components. Finally, call power_supply_changed() once and
lead to a single uevent instead of a bunch, preventing userspace
programs from causing too much pressure on power supply properties and
underlying ACPI methods.

If more than 16 battery notifications are queued within 10ms, the
firmware/hardware is anyway buggy, and extra notifications will be
dropped.

Tested-by: Jeffrey Wälti <jeffrey@waelti.dev>
Tested-by: Avraham Hollander <anhollander516@gmail.com>
Reported-by: Rick <rickk1166@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221065
Signed-off-by: Rong Zhang <i@rong.moe>
---
Changes in v4:
- Rebase and adopt devres-based resource management
- Refactor acpi_battery_notify() to hold the mutex across the entire
  function to improve readability and drop unnecessary variables (thanks
  Rafael J. Wysocki)

Changes in v2:
- Address Sashiko's concerns:
  - Return from acpi_battery_notification_worker() early when the fifo
    is empty
  - Use pr_err_ratelimited() for potential event storms
  - Add missing `\n' in a printk message
  - https://sashiko.dev/#/patchset/20260527-b4-acpi-battery-notification-v1-0-2303bed8ec0b%40rong.moe
- Minimalize the critical section of acpi_battery_notify()
---
 drivers/acpi/battery.c | 89 +++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 80 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index f5e0eb299610..8b26962745bd 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -14,6 +14,7 @@
 #include <linux/dmi.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
+#include <linux/kfifo.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -21,6 +22,7 @@
 #include <linux/slab.h>
 #include <linux/suspend.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 
 #include <linux/unaligned.h>
 
@@ -43,6 +45,9 @@
 
 #define MAX_STRING_LENGTH	64
 
+#define MAX_QUEUED_EVENTS	16
+#define NOTIF_MERGING_MS	10
+
 MODULE_AUTHOR("Paul Diefenbaugh");
 MODULE_AUTHOR("Alexey Starikovskiy <astarikovskiy@suse.de>");
 MODULE_DESCRIPTION("ACPI Battery Driver");
@@ -95,6 +100,8 @@ struct acpi_battery {
 	struct power_supply_desc bat_desc;
 	struct acpi_device *device;
 	struct device *phys_dev;
+	struct kfifo acpi_notif_fifo;
+	struct delayed_work acpi_notif_dwork;
 	struct notifier_block pm_nb;
 	struct list_head list;
 	unsigned long update_time;
@@ -1059,14 +1066,24 @@ static void acpi_battery_refresh(struct acpi_battery *battery)
 }
 
 /* Driver Interface */
-static void acpi_battery_notify(acpi_handle handle, u32 event, void *data)
+static void acpi_battery_notification_worker(struct work_struct *work)
 {
-	struct acpi_battery *battery = data;
+	struct acpi_battery *battery = container_of(work, struct acpi_battery,
+						    acpi_notif_dwork.work);
 	struct acpi_device *device = battery->device;
+	u32 events[MAX_QUEUED_EVENTS];
 	struct power_supply *old;
+	unsigned int count, i;
 
 	guard(mutex)(&battery->update_lock);
 
+	count = kfifo_out(&battery->acpi_notif_fifo, events, sizeof(events));
+	count /= sizeof(events[0]);
+	if (!count)
+		return;
+
+	pr_debug("merged %u battery notifications within %dms\n", count, NOTIF_MERGING_MS);
+
 	old = battery->bat;
 	/*
 	 * On Acer Aspire V5-573G notifications are sometimes triggered too
@@ -1076,19 +1093,46 @@ static void acpi_battery_notify(acpi_handle handle, u32 event, void *data)
 	 */
 	if (battery_notification_delay_ms > 0)
 		msleep(battery_notification_delay_ms);
-	if (event == ACPI_BATTERY_NOTIFY_INFO)
-		acpi_battery_refresh(battery);
+
+	for (i = 0; i < count; i++) {
+		if (events[i] == ACPI_BATTERY_NOTIFY_INFO) {
+			acpi_battery_refresh(battery);
+			break;
+		}
+	}
+
 	acpi_battery_update(battery, false);
-	acpi_bus_generate_netlink_event(ACPI_BATTERY_CLASS,
-					dev_name(&device->dev), event,
-					acpi_battery_present(battery));
-	acpi_notifier_call_chain(ACPI_BATTERY_CLASS, acpi_device_bid(device),
-				 event, acpi_battery_present(battery));
+
+	for (i = 0; i < count; i++) {
+		acpi_bus_generate_netlink_event(ACPI_BATTERY_CLASS,
+						dev_name(&device->dev), events[i],
+						acpi_battery_present(battery));
+		acpi_notifier_call_chain(ACPI_BATTERY_CLASS, acpi_device_bid(device),
+					 events[i], acpi_battery_present(battery));
+	}
+
 	/* acpi_battery_update could remove power_supply object */
 	if (old && battery->bat)
 		power_supply_changed(battery->bat);
 }
 
+static void acpi_battery_notify(acpi_handle handle, u32 event, void *data)
+{
+	struct acpi_battery *battery = data;
+
+	guard(mutex)(&battery->update_lock);
+
+	if (kfifo_avail(&battery->acpi_notif_fifo) >= sizeof(event)) {
+		kfifo_in(&battery->acpi_notif_fifo, &event, sizeof(event));
+		schedule_delayed_work(&battery->acpi_notif_dwork,
+				      msecs_to_jiffies(NOTIF_MERGING_MS));
+
+		return;
+	}
+
+	pr_err_ratelimited("too many battery notifications within %dms\n", NOTIF_MERGING_MS);
+}
+
 static int battery_notify(struct notifier_block *nb,
 			  unsigned long mode, void *_unused)
 {
@@ -1231,6 +1275,29 @@ static int devm_acpi_battery_update_retry(struct device *dev,
 	return ret;
 }
 
+static void acpi_battery_notify_dwork_cleanup(void *data)
+{
+	struct acpi_battery *battery = data;
+
+	cancel_delayed_work_sync(&battery->acpi_notif_dwork);
+	kfifo_free(&battery->acpi_notif_fifo);
+}
+
+static int devm_acpi_battery_init_notify_dwork(struct device *dev,
+					       struct acpi_battery *battery)
+{
+	int ret;
+
+	INIT_DELAYED_WORK(&battery->acpi_notif_dwork, acpi_battery_notification_worker);
+
+	ret = kfifo_alloc(&battery->acpi_notif_fifo,
+			  MAX_QUEUED_EVENTS * sizeof(u32), GFP_KERNEL);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, acpi_battery_notify_dwork_cleanup, battery);
+}
+
 static int acpi_battery_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -1272,6 +1339,10 @@ static int acpi_battery_probe(struct platform_device *pdev)
 	if (result)
 		return result;
 
+	result = devm_acpi_battery_init_notify_dwork(dev, battery);
+	if (result)
+		return result;
+
 	result = devm_acpi_install_notify_handler(dev, ACPI_ALL_NOTIFY,
 						  acpi_battery_notify, battery);
 	if (result)

-- 
2.53.0

[PATCH v4 2/3] ACPI: battery: Use kstrtoul() over sscanf("%lu\n")

[Rong Zhang]

It is more preferred to use kstrto*() to parse a single number. The
function family properly returns an errno on error and is the correct
mechanism to parse data from sysfs.

The number base is set to 10 in order not to break the ABI.

Tested-by: Avraham Hollander <anhollander516@gmail.com>
Signed-off-by: Rong Zhang <i@rong.moe>
---
Changes in v3:
- Address Sashiko's concerns on my last-minute changes:
  - Set the number base to 10 in order not to break the ABI
  - https://sashiko.dev/#/patchset/20260611-b4-acpi-battery-notification-v2-0-4e8ed651a151%40rong.moe

Changes in v2:
- New patch in series
  - Since the series touches acpi_battery_alarm_store(), also convert
    the use of sscanf("%lu\n") into the more preferred kstrtoul()
    beforehand
---
 drivers/acpi/battery.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index 8b26962745bd..bd7fa93ff16f 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -675,9 +675,13 @@ static ssize_t acpi_battery_alarm_store(struct device *dev,
 {
 	unsigned long x;
 	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
+	int err;
 
-	if (sscanf(buf, "%lu\n", &x) == 1)
-		battery->alarm = x/1000;
+	err = kstrtoul(buf, 10, &x);
+	if (err)
+		return err;
+
+	battery->alarm = x / 1000;
 	if (acpi_battery_present(battery))
 		acpi_battery_set_alarm(battery);
 	return count;

-- 
2.53.0

[PATCH v4 3/3] ACPI: battery: Protect all properties with a separated mutex

[Rong Zhang]

The acpi_battery_get_property() callback calls acpi_battery_get_state()
without any lock held, which could lead to race conditions, e.g., when
multiple tasks read power supply properties simultaneously, or when
other callbacks are called during its execution.

Moreover, some devices' _BST method relies on a heavily shared ACPI
mutex which protects EC accesses, so it cannot tolerate too much
pressure or else other methods will time out. The lack of
synchronization sometimes nullifies the cache mechanism of
acpi_battery_get_state() when multiple processes read power supply
properties simultaneously, which usually happens after a uevent.
Normally, emitting a uevent implies that the cache must have been
refreshed due to power_supply_uevent() reading all properties, so the
mentioned processes should have seen cache hits. Unfortunately, these
fragile devices' power_supply_ext properties are somehow slow to read
after battery events, resulting in cache expiration before
power_supply_uevent() finishes. Hence, once the uevent reaches
userspace, the _BST method will be executed multiple times within a
short period due to userspace processes reading all properties again.
The coincidence causes lock starvation, resulting in a catastrophic
situation that a lot of ACPI methods fail to acquire the shared ACPI
mutex due to timeout and return garbage data thanks to the firmware's
poorly designed error paths.

The said "other synchronized methods" are protected by update_lock,
leaving acpi_battery_get_property() to be the last desynchronized code
path. Unfortunately, update_lock is not applicapable for
acpi_battery_get_property(), as it protects too many fields, far more
than necessary. What's worse, some code path could call or wait for
acpi_battery_get_property() while an outer functions holding
update_lock.

Therefore, introduce a mutex to protect all accesses to battery
properties, so that acpi_battery_get_property() can take the advantage
of the mutex and synchronize itself. The helper function
acpi_battery_handle_discharging() for quirky devices has to be inlined
due to the change, as the mutex must be unlocked before calling the
expensive power_supply_is_system_supplied() helper function.

Tested-by: Avraham Hollander <anhollander516@gmail.com>
Reported-by: Rick <rickk1166@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221065
Signed-off-by: Rong Zhang <i@rong.moe>
---
Changes in v3:
- Address Sashiko's concerns on my last-minute changes:
  - Do not overwrite the initial value of `ret' in
    acpi_battery_get_property()
  - https://sashiko.dev/#/patchset/20260611-b4-acpi-battery-notification-v2-0-4e8ed651a151%40rong.moe

Changes in v2:
- Address Sashiko's concerns:
  - Use a separated mutex to protect all properties instead of reusing
    update_lock
  - https://sashiko.dev/#/patchset/20260527-b4-acpi-battery-notification-v1-0-2303bed8ec0b%40rong.moe
- Dropped Tested-by due to massive rewrite
---
 drivers/acpi/battery.c | 147 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 101 insertions(+), 46 deletions(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index bd7fa93ff16f..3ad4acf3d44d 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/kfifo.h>
 #include <linux/list.h>
+#include <linux/lockdep.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/platform_device.h>
@@ -104,6 +105,9 @@ struct acpi_battery {
 	struct delayed_work acpi_notif_dwork;
 	struct notifier_block pm_nb;
 	struct list_head list;
+	unsigned long flags;
+
+	struct mutex property_lock; /* Protects properties below. */
 	unsigned long update_time;
 	int revision;
 	int rate_now;
@@ -130,7 +134,6 @@ struct acpi_battery {
 	char oem_info[MAX_STRING_LENGTH];
 	int state;
 	int power_unit;
-	unsigned long flags;
 };
 
 #define to_acpi_battery(x) power_supply_get_drvdata(x)
@@ -187,20 +190,6 @@ static bool acpi_battery_is_degraded(struct acpi_battery *battery)
 		battery->full_charge_capacity < battery->design_capacity;
 }
 
-static int acpi_battery_handle_discharging(struct acpi_battery *battery)
-{
-	/*
-	 * Some devices wrongly report discharging if the battery's charge level
-	 * was above the device's start charging threshold atm the AC adapter
-	 * was plugged in and the device thus did not start a new charge cycle.
-	 */
-	if ((battery_ac_is_broken || power_supply_is_system_supplied()) &&
-	    battery->rate_now == 0)
-		return POWER_SUPPLY_STATUS_NOT_CHARGING;
-
-	return POWER_SUPPLY_STATUS_DISCHARGING;
-}
-
 static int acpi_battery_get_property(struct power_supply *psy,
 				     enum power_supply_property psp,
 				     union power_supply_propval *val)
@@ -208,15 +197,41 @@ static int acpi_battery_get_property(struct power_supply *psy,
 	int full_capacity = ACPI_BATTERY_VALUE_UNKNOWN, ret = 0;
 	struct acpi_battery *battery = to_acpi_battery(psy);
 
-	if (acpi_battery_present(battery)) {
-		/* run battery update only if it is present */
-		acpi_battery_get_state(battery);
-	} else if (psp != POWER_SUPPLY_PROP_PRESENT)
-		return -ENODEV;
+	/* run battery update only if it is present */
+	if (!acpi_battery_present(battery)) {
+		switch (psp) {
+		case POWER_SUPPLY_PROP_PRESENT:
+			val->intval = 0;
+			return 0;
+		default:
+			return -ENODEV;
+		}
+	}
+
+	mutex_lock(&battery->property_lock);
+
+	acpi_battery_get_state(battery);
+
 	switch (psp) {
 	case POWER_SUPPLY_PROP_STATUS:
+		/*
+		 * Some devices wrongly report discharging if the battery's charge level
+		 * was above the device's start charging threshold atm the AC adapter
+		 * was plugged in and the device thus did not start a new charge cycle.
+		 */
 		if (battery->state & ACPI_BATTERY_STATE_DISCHARGING)
-			val->intval = acpi_battery_handle_discharging(battery);
+			if (battery->rate_now != 0) {
+				val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+			} else if (battery_ac_is_broken) {
+				val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
+			} else {
+				mutex_unlock(&battery->property_lock);
+
+				val->intval = power_supply_is_system_supplied()
+					? POWER_SUPPLY_STATUS_NOT_CHARGING
+					: POWER_SUPPLY_STATUS_DISCHARGING;
+				return 0;
+			}
 		else if (battery->state & ACPI_BATTERY_STATE_CHARGING)
 			/* Validate the status by checking the current. */
 			if (battery->rate_now != ACPI_BATTERY_VALUE_UNKNOWN &&
@@ -318,6 +333,8 @@ static int acpi_battery_get_property(struct power_supply *psy,
 	default:
 		ret = -EINVAL;
 	}
+
+	mutex_unlock(&battery->property_lock);
 	return ret;
 }
 
@@ -540,6 +557,8 @@ static int acpi_battery_get_info(struct acpi_battery *battery)
 	int use_bix;
 	int result = -ENODEV;
 
+	lockdep_assert_held(&battery->property_lock);
+
 	if (!acpi_battery_present(battery))
 		return 0;
 
@@ -579,6 +598,8 @@ static int acpi_battery_get_state(struct acpi_battery *battery)
 	acpi_status status = 0;
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
 
+	lockdep_assert_held(&battery->property_lock);
+
 	if (!acpi_battery_present(battery))
 		return 0;
 
@@ -632,6 +653,8 @@ static int acpi_battery_set_alarm(struct acpi_battery *battery)
 {
 	acpi_status status = 0;
 
+	lockdep_assert_held(&battery->property_lock);
+
 	if (!acpi_battery_present(battery) ||
 	    !test_bit(ACPI_BATTERY_ALARM_PRESENT, &battery->flags))
 		return -ENODEV;
@@ -649,6 +672,8 @@ static int acpi_battery_set_alarm(struct acpi_battery *battery)
 
 static int acpi_battery_init_alarm(struct acpi_battery *battery)
 {
+	lockdep_assert_held(&battery->property_lock);
+
 	/* See if alarms are supported, and if so, set default */
 	if (!acpi_has_method(battery->device->handle, "_BTP")) {
 		clear_bit(ACPI_BATTERY_ALARM_PRESENT, &battery->flags);
@@ -666,6 +691,8 @@ static ssize_t acpi_battery_alarm_show(struct device *dev,
 {
 	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
 
+	guard(mutex)(&battery->property_lock);
+
 	return sysfs_emit(buf, "%d\n", battery->alarm * 1000);
 }
 
@@ -681,6 +708,8 @@ static ssize_t acpi_battery_alarm_store(struct device *dev,
 	if (err)
 		return err;
 
+	guard(mutex)(&battery->property_lock);
+
 	battery->alarm = x / 1000;
 	if (acpi_battery_present(battery))
 		acpi_battery_set_alarm(battery);
@@ -865,12 +894,17 @@ static int sysfs_add_battery(struct acpi_battery *battery)
 		.no_wakeup_source = true,
 	};
 	bool full_cap_broken = false;
+	int power_unit;
 
-	if (!ACPI_BATTERY_CAPACITY_VALID(battery->full_charge_capacity) &&
-	    !ACPI_BATTERY_CAPACITY_VALID(battery->design_capacity))
-		full_cap_broken = true;
+	scoped_guard(mutex, &battery->property_lock) {
+		power_unit = battery->power_unit;
 
-	if (battery->power_unit == ACPI_BATTERY_POWER_UNIT_MA) {
+		if (!ACPI_BATTERY_CAPACITY_VALID(battery->full_charge_capacity) &&
+		    !ACPI_BATTERY_CAPACITY_VALID(battery->design_capacity))
+			full_cap_broken = true;
+	}
+
+	if (power_unit == ACPI_BATTERY_POWER_UNIT_MA) {
 		if (full_cap_broken) {
 			battery->bat_desc.properties =
 			    charge_battery_full_cap_broken_props;
@@ -924,6 +958,9 @@ static void sysfs_remove_battery(struct acpi_battery *battery)
 static void find_battery(const struct dmi_header *dm, void *private)
 {
 	struct acpi_battery *battery = (struct acpi_battery *)private;
+
+	lockdep_assert_held(&battery->property_lock);
+
 	/* Note: the hardcoded offsets below have been extracted from
 	 * the source code of dmidecode.
 	 */
@@ -955,6 +992,8 @@ static void find_battery(const struct dmi_header *dm, void *private)
  */
 static void acpi_battery_quirks(struct acpi_battery *battery)
 {
+	lockdep_assert_held(&battery->property_lock);
+
 	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags))
 		return;
 
@@ -1007,30 +1046,38 @@ static void acpi_battery_quirks(struct acpi_battery *battery)
 static int acpi_battery_update(struct acpi_battery *battery, bool resume)
 {
 	int result = acpi_battery_get_status(battery);
+	bool wakeup;
 
 	if (result)
 		return result;
 
 	if (!acpi_battery_present(battery)) {
 		sysfs_remove_battery(battery);
-		battery->update_time = 0;
+		scoped_guard(mutex, &battery->property_lock)
+			battery->update_time = 0;
 		return 0;
 	}
 
 	if (resume)
 		return 0;
 
-	if (!battery->update_time) {
-		result = acpi_battery_get_info(battery);
+	scoped_guard(mutex, &battery->property_lock) {
+		if (!battery->update_time) {
+			result = acpi_battery_get_info(battery);
+			if (result)
+				return result;
+			acpi_battery_init_alarm(battery);
+		}
+
+		result = acpi_battery_get_state(battery);
 		if (result)
 			return result;
-		acpi_battery_init_alarm(battery);
-	}
+		acpi_battery_quirks(battery);
 
-	result = acpi_battery_get_state(battery);
-	if (result)
-		return result;
-	acpi_battery_quirks(battery);
+		wakeup = ((battery->state & ACPI_BATTERY_STATE_CRITICAL) ||
+			  (test_bit(ACPI_BATTERY_ALARM_PRESENT, &battery->flags) &&
+			   (battery->capacity_now <= battery->alarm)));
+	}
 
 	if (!battery->bat) {
 		result = sysfs_add_battery(battery);
@@ -1042,9 +1089,7 @@ static int acpi_battery_update(struct acpi_battery *battery, bool resume)
 	 * Wakeup the system if battery is critical low
 	 * or lower than the alarm level
 	 */
-	if ((battery->state & ACPI_BATTERY_STATE_CRITICAL) ||
-	    (test_bit(ACPI_BATTERY_ALARM_PRESENT, &battery->flags) &&
-	     (battery->capacity_now <= battery->alarm)))
+	if (wakeup)
 		acpi_pm_wakeup_event(battery->phys_dev);
 
 	return result;
@@ -1057,12 +1102,14 @@ static void acpi_battery_refresh(struct acpi_battery *battery)
 	if (!battery->bat)
 		return;
 
-	power_unit = battery->power_unit;
+	scoped_guard(mutex, &battery->property_lock) {
+		power_unit = battery->power_unit;
 
-	acpi_battery_get_info(battery);
+		acpi_battery_get_info(battery);
 
-	if (power_unit == battery->power_unit)
-		return;
+		if (power_unit == battery->power_unit)
+			return;
+	}
 
 	/* The battery has changed its reporting units. */
 	sysfs_remove_battery(battery);
@@ -1154,17 +1201,21 @@ static int battery_notify(struct notifier_block *nb,
 		} else {
 			int result;
 
-			result = acpi_battery_get_info(battery);
-			if (result)
-				return result;
+			scoped_guard(mutex, &battery->property_lock) {
+				result = acpi_battery_get_info(battery);
+				if (result)
+					return result;
+			}
 
 			result = sysfs_add_battery(battery);
 			if (result)
 				return result;
 		}
 
-		acpi_battery_init_alarm(battery);
-		acpi_battery_get_state(battery);
+		scoped_guard(mutex, &battery->property_lock) {
+			acpi_battery_init_alarm(battery);
+			acpi_battery_get_state(battery);
+		}
 	}
 
 	return 0;
@@ -1329,6 +1380,10 @@ static int acpi_battery_probe(struct platform_device *pdev)
 	if (result)
 		return result;
 
+	result = devm_mutex_init(&pdev->dev, &battery->property_lock);
+	if (result)
+		return result;
+
 	if (acpi_has_method(battery->device->handle, "_BIX"))
 		set_bit(ACPI_BATTERY_XINFO_PRESENT, &battery->flags);
 

-- 
2.53.0