ACPI: thermal: Do not call acpi_thermal_check() directly

BugLink: https://bugs.launchpad.net/bugs/1916061
commit 81b704d3e4674e09781d331df73d76675d5ad8cb upstream.

Calling acpi_thermal_check() from acpi_thermal_notify() directly
is problematic if _TMP triggers Notify () on the thermal zone for
which it has been evaluated (which happens on some systems), because
it causes a new acpi_thermal_notify() invocation to be queued up
every time and if that takes place too often, an indefinite number of
pending work items may accumulate in kacpi_notify_wq over time.

Besides, it is not really useful to queue up a new invocation of
acpi_thermal_check() if one of them is pending already.

For these reasons, rework acpi_thermal_notify() to queue up a thermal
check instead of calling acpi_thermal_check() directly and only allow
one thermal check to be pending at a time.  Moreover, only allow one
acpi_thermal_check_fn() instance at a time to run
thermal_zone_device_update() for one thermal zone and make it return
early if it sees other instances running for the same thermal zone.

While at it, fold acpi_thermal_check() into acpi_thermal_check_fn(),
as it is only called from there after the other changes made here.

[This issue appears to have been exposed by commit 6d25be5782e4
 ("sched/core, workqueues: Distangle worker accounting from rq
 lock"), but it is unclear why it was not visible earlier.]

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=208877
Reported-by: Stephen Berman <stephen.berman@gmx.net>
Diagnosed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Stephen Berman <stephen.berman@gmx.net>
Cc: All applicable <stable@vger.kernel.org>
[bigeasy: Backported to v5.4.y]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index d831a61e0010eaf69dd16c96f0983315cf0a0972..383c7029d3cee04b60fa3de395cad5b683e7cf8c 100644 (file)
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -174,6 +174,8 @@ struct acpi_thermal {
        int tz_enabled;
        int kelvin_offset;
        struct work_struct thermal_check_work;
+       struct mutex thermal_check_lock;
+       refcount_t thermal_check_count;
 };
 
 /* --------------------------------------------------------------------------
@@ -494,17 +496,6 @@ static int acpi_thermal_get_trip_points(struct acpi_thermal *tz)
        return 0;
 }
 
-static void acpi_thermal_check(void *data)
-{
-       struct acpi_thermal *tz = data;
-
-       if (!tz->tz_enabled)
-               return;
-
-       thermal_zone_device_update(tz->thermal_zone,
-                                  THERMAL_EVENT_UNSPECIFIED);
-}
-
 /* sys I/F for generic thermal sysfs support */
 
 static int thermal_get_temp(struct thermal_zone_device *thermal, int *temp)
@@ -538,6 +529,8 @@ static int thermal_get_mode(struct thermal_zone_device *thermal,
        return 0;
 }
 
+static void acpi_thermal_check_fn(struct work_struct *work);
+
 static int thermal_set_mode(struct thermal_zone_device *thermal,
                                enum thermal_device_mode mode)
 {
@@ -563,7 +556,7 @@ static int thermal_set_mode(struct thermal_zone_device *thermal,
                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                        "%s kernel ACPI thermal control\n",
                        tz->tz_enabled ? "Enable" : "Disable"));
-               acpi_thermal_check(tz);
+               acpi_thermal_check_fn(&tz->thermal_check_work);
        }
        return 0;
 }
@@ -932,6 +925,12 @@ static void acpi_thermal_unregister_thermal_zone(struct acpi_thermal *tz)
                                  Driver Interface
    -------------------------------------------------------------------------- */
 
+static void acpi_queue_thermal_check(struct acpi_thermal *tz)
+{
+       if (!work_pending(&tz->thermal_check_work))
+               queue_work(acpi_thermal_pm_queue, &tz->thermal_check_work);
+}
+
 static void acpi_thermal_notify(struct acpi_device *device, u32 event)
 {
        struct acpi_thermal *tz = acpi_driver_data(device);
@@ -942,17 +941,17 @@ static void acpi_thermal_notify(struct acpi_device *device, u32 event)
 
        switch (event) {
        case ACPI_THERMAL_NOTIFY_TEMPERATURE:
-               acpi_thermal_check(tz);
+               acpi_queue_thermal_check(tz);
                break;
        case ACPI_THERMAL_NOTIFY_THRESHOLDS:
                acpi_thermal_trips_update(tz, ACPI_TRIPS_REFRESH_THRESHOLDS);
-               acpi_thermal_check(tz);
+               acpi_queue_thermal_check(tz);
                acpi_bus_generate_netlink_event(device->pnp.device_class,
                                                  dev_name(&device->dev), event, 0);
                break;
        case ACPI_THERMAL_NOTIFY_DEVICES:
                acpi_thermal_trips_update(tz, ACPI_TRIPS_REFRESH_DEVICES);
-               acpi_thermal_check(tz);
+               acpi_queue_thermal_check(tz);
                acpi_bus_generate_netlink_event(device->pnp.device_class,
                                                  dev_name(&device->dev), event, 0);
                break;
@@ -1052,7 +1051,27 @@ static void acpi_thermal_check_fn(struct work_struct *work)
 {
        struct acpi_thermal *tz = container_of(work, struct acpi_thermal,
                                               thermal_check_work);
-       acpi_thermal_check(tz);
+
+       if (!tz->tz_enabled)
+               return;
+       /*
+        * In general, it is not sufficient to check the pending bit, because
+        * subsequent instances of this function may be queued after one of them
+        * has started running (e.g. if _TMP sleeps).  Avoid bailing out if just
+        * one of them is running, though, because it may have done the actual
+        * check some time ago, so allow at least one of them to block on the
+        * mutex while another one is running the update.
+        */
+       if (!refcount_dec_not_one(&tz->thermal_check_count))
+               return;
+
+       mutex_lock(&tz->thermal_check_lock);
+
+       thermal_zone_device_update(tz->thermal_zone, THERMAL_EVENT_UNSPECIFIED);
+
+       refcount_inc(&tz->thermal_check_count);
+
+       mutex_unlock(&tz->thermal_check_lock);
 }
 
 static int acpi_thermal_add(struct acpi_device *device)
@@ -1084,6 +1103,8 @@ static int acpi_thermal_add(struct acpi_device *device)
        if (result)
                goto free_memory;
 
+       refcount_set(&tz->thermal_check_count, 3);
+       mutex_init(&tz->thermal_check_lock);
        INIT_WORK(&tz->thermal_check_work, acpi_thermal_check_fn);
 
        pr_info(PREFIX "%s [%s] (%ld C)\n", acpi_device_name(device),
@@ -1149,7 +1170,7 @@ static int acpi_thermal_resume(struct device *dev)
                tz->state.active |= tz->trips.active[i].flags.enabled;
        }
 
-       queue_work(acpi_thermal_pm_queue, &tz->thermal_check_work);
+       acpi_queue_thermal_check(tz);
 
        return AE_OK;
 }