The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 81b704d3e4674e09781d331df73d76675d5ad8cb Mon Sep 17 00:00:00 2001

From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Date: Thu, 14 Jan 2021 19:34:22 +0100 Subject: [PATCH] ACPI: thermal: Do not call acpi_thermal_check() directly

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

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c index 12c0ece746f0..859b1de31ddc 100644 --- a/drivers/acpi/thermal.c +++ b/drivers/acpi/thermal.c @@ -174,6 +174,8 @@ struct acpi_thermal { struct thermal_zone_device *thermal_zone; int kelvin_offset; /* in millidegrees */ struct work_struct thermal_check_work; + struct mutex thermal_check_lock; + refcount_t thermal_check_count; };

/* -------------------------------------------------------------------------- @@ -495,14 +497,6 @@ 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; - - 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) @@ -900,6 +894,12 @@ 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); @@ -910,17 +910,17 @@ 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; @@ -1020,7 +1020,25 @@ 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); + + /* + * 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) @@ -1052,6 +1070,8 @@ 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), @@ -1117,7 +1137,7 @@ 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; }