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  1. 28 Dec, 2023 1 commit
    • Rafael J. Wysocki's avatar
      thermal: core: Fix thermal zone suspend-resume synchronization · 4e814173
      Rafael J. Wysocki authored 
      There are 3 synchronization issues with thermal zone suspend-resume
during system-wide transitions:

 1. The resume code runs in a PM notifier which is invoked after user
    space has been thawed, so it can run concurrently with user space
    which can trigger a thermal zone device removal.  If that happens,
    the thermal zone resume code may use a stale pointer to the next
    list element and crash, because it does not hold thermal_list_lock
    while walking thermal_tz_list.

 2. The thermal zone resume code calls thermal_zone_device_init()
    outside the zone lock, so user space or an update triggered by
    the platform firmware may see an inconsistent state of a
    thermal zone leading to unexpected behavior.

 3. Clearing the in_suspend global variable in thermal_pm_notify()
    allows __thermal_zone_device_update() to continue for all thermal
    zones and it may as well run before the thermal_tz_list walk (or
    at any point during the list walk for that matter) and attempt to
    operate on a thermal zone that has not been resumed yet.  It may
    also race destructively with thermal_zone_device_init().

To address these issues, add thermal_list_lock locking to
thermal_pm_notify(), especially arount the thermal_tz_list,
make it call thermal_zone_device_init() back-to-back with
__thermal_zone_device_update() under the zone lock and replace
in_suspend with per-zone bool "suspend" indicators set and unset
under the given zone's lock.

Link: https://lore.kernel.org/linux-pm/20231218162348.69101-1-bo.ye@mediatek.com/Reported-by: default avatarBo Ye <bo.ye@mediatek.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      4e814173
  3. 21 Dec, 2023 1 commit
  5. 15 Dec, 2023 1 commit
    • Rafael J. Wysocki's avatar
      thermal: core: Fix NULL pointer dereference in zone registration error path · 04e6ccfc
      Rafael J. Wysocki authored 
      If device_register() in thermal_zone_device_register_with_trips()
returns an error, the tz variable is set to NULL and subsequently
dereferenced in kfree(tz->tzp).

Commit adc8749b ("thermal/drivers/core: Use put_device() if
device_register() fails") added the tz = NULL assignment in question to
avoid a possible double-free after dropping the reference to the zone
device.  However, after commit 4649620d ("thermal: core: Make
thermal_zone_device_unregister() return after freeing the zone"), that
assignment has become redundant, because dropping the reference to the
zone device does not cause the zone object to be freed any more.

Drop it to address the NULL pointer dereference.

Fixes: 3d439b1a ("thermal/core: Alloc-copy-free the thermal zone parameters structure")
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarLukasz Luba <lukasz.luba@arm.com>
      04e6ccfc
  7. 13 Dec, 2023 6 commits
  9. 12 Dec, 2023 2 commits
    • Rafael J. Wysocki's avatar
      thermal: core: Rework thermal zone availability check · b38aa87f
      Rafael J. Wysocki authored 
      In order to avoid running __thermal_zone_device_update() for thermal
zones going away, the thermal zone lock is held around device_del()
in thermal_zone_device_unregister() and thermal_zone_device_update()
passes the given thermal zone device to device_is_registered().
This allows thermal_zone_device_update() to skip the
__thermal_zone_device_update() if device_del() has already run for
the thermal zone at hand.

However, instead of looking at driver core internals, the thermal
subsystem may as well rely on its own data structures for this
purpose.  Namely, if the thermal zone is not present in
thermal_tz_list, it can be regarded as unavailable, which in fact is
already the case in thermal_zone_device_unregister().  Accordingly,
the device_is_registered() check in thermal_zone_device_update() can
be replaced with checking whether or not the node list_head in struct
thermal_zone_device is empty, in which case it is not there in
thermal_tz_list.

To make this work, though, it is necessary to initialize tz->node
in thermal_zone_device_register_with_trips() before registering the
thermal zone device and it needs to be added to thermal_tz_list and
deleted from it under its zone lock.

After the above modifications, the zone lock does not need to be
held around device_del() in thermal_zone_device_unregister() any more.
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-and-tested-by: default avatarLukasz Luba <lukasz.luba@arm.com>
Acked-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
      b38aa87f
    • Rafael J. Wysocki's avatar
      thermal: Drop redundant and confusing device_is_registered() checks · c3ffdfff
      Rafael J. Wysocki authored 
      Multiple places in the thermal subsystem (most importantly, sysfs
attribute callback functions) check if the given thermal zone device is
still registered in order to return early in case the device_del() in
thermal_zone_device_unregister() has run already.

However, after thermal_zone_device_unregister() has been made wait for
all of the zone-related activity to complete before returning, it is
not necessary to do that any more, because all of the code holding a
reference to the thermal zone device object will be waited for even if
it does not do anything special to enforce this.

Accordingly, drop all of the device_is_registered() checks that are now
redundant and get rid of the zone locking that is not necessary any more
after dropping them.
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-and-tested-by: default avatarLukasz Luba <lukasz.luba@arm.com>
Acked-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
      c3ffdfff
  11. 11 Dec, 2023 1 commit
  13. 06 Dec, 2023 2 commits
    • Rafael J. Wysocki's avatar
      thermal: sysfs: Rework the reading of trip point attributes · 18dfb0e4
      Rafael J. Wysocki authored 
      Rework the _show() callback functions for the trip point temperature,
hysteresis and type attributes to avoid copying the values of struct
thermal_trip fields that they do not use and make them carry out the
same validation checks as the corresponding _store() callback functions.

No intentional functional impact.
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
      18dfb0e4
    • Rafael J. Wysocki's avatar
      thermal: sysfs: Rework the handling of trip point updates · be0a3600
      Rafael J. Wysocki authored 
      Both trip_point_temp_store() and trip_point_hyst_store() use
thermal_zone_set_trip() to update a given trip point, but none of them
actually needs to change more than one field in struct thermal_trip
representing it.  However, each of them effectively calls
__thermal_zone_get_trip() twice in a row for the same trip index value,
once directly and once via thermal_zone_set_trip(), which is not
particularly efficient, and the way in which thermal_zone_set_trip()
carries out the update is not particularly straightforward.

Moreover, input processing need not be done under the thermal zone lock
in any of these functions.

Rework trip_point_temp_store() and trip_point_hyst_store() to address
the above, move the part of thermal_zone_set_trip() that is still
useful to a new function called thermal_zone_trip_updated() and drop
the rest of it.

While at it, make trip_point_hyst_store() reject negative hysteresis
values.
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
      be0a3600
  15. 30 Nov, 2023 1 commit
  17. 28 Nov, 2023 7 commits
  19. 20 Nov, 2023 1 commit
    • Rafael J. Wysocki's avatar
      thermal: core: Add trip thresholds for trip crossing detection · 44844db9
      Rafael J. Wysocki authored 
      The trip crossing detection in handle_thermal_trip() does not work
correctly in the cases when a trip point is crossed on the way up and
then the zone temperature stays above its low temperature (that is, its
temperature decreased by its hysteresis).  The trip temperature may
be passed by the zone temperature subsequently in that case, even
multiple times, but that does not count as the trip crossing as long as
the zone temperature does not fall below the trip's low temperature or,
in other words, until the trip is crossed on the way down.

|-----------low--------high------------|
             |<--------->|
             |    hyst   |
             |           |
             |          -|--> crossed on the way up
             |
         <---|-- crossed on the way down

However, handle_thermal_trip() will invoke thermal_notify_tz_trip_up()
every time the trip temperature is passed by the zone temperature on
the way up regardless of whether or not the trip has been crossed on
the way down yet.  Moreover, it will not call thermal_notify_tz_trip_down()
if the last zone temperature was between the trip's temperature and its
low temperature, so some "trip crossed on the way down" events may not
be reported.

To address this issue, introduce trip thresholds equal to either the
temperature of the given trip, or its low temperature, such that if
the trip's threshold is passed by the zone temperature on the way up,
its value will be set to the trip's low temperature and
thermal_notify_tz_trip_up() will be called, and if the trip's threshold
is passed by the zone temperature on the way down, its value will be set
to the trip's temperature (high) and thermal_notify_tz_trip_down() will
be called.  Accordingly, if the threshold is passed on the way up, it
cannot be passed on the way up again until its passed on the way down
and if it is passed on the way down, it cannot be passed on the way down
again until it is passed on the way up which guarantees correct
triggering of trip crossing notifications.

If the last temperature of the zone is invalid, the trip's threshold
will be set depending of the zone's current temperature: If that
temperature is above the trip's temperature, its threshold will be
set to its low temperature or otherwise its threshold will be set to
its (high) temperature.  Because the zone temperature is initially
set to invalid and tz->last_temperature is only updated by
update_temperature(), this is sufficient to set the correct initial
threshold values for all trips.

Link: https://lore.kernel.org/all/20220718145038.1114379-4-daniel.lezcano@linaro.orgSigned-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      44844db9
  21. 19 Nov, 2023 8 commits
  23. 18 Nov, 2023 9 commits
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