1. 23 11月, 2016 28 次提交
  2. 27 9月, 2016 3 次提交
  3. 08 8月, 2016 1 次提交
    • M
      thermal: fix race condition when updating cooling device · d0b7306d
      Michele Di Giorgio 提交于
      When multiple thermal zones are bound to the same cooling device, multiple
      kernel threads may want to update the cooling device state by calling
      thermal_cdev_update(). Having cdev not protected by a mutex can lead to a race
      condition. Consider the following situation with two kernel threads k1 and k2:
      
      	    Thread k1				Thread k2
                                          ||
                                          ||  call thermal_cdev_update()
                                          ||      ...
                                          ||      set_cur_state(cdev, target);
          call power_actor_set_power()    ||
              ...                         ||
              instance->target = state;   ||
              cdev->updated = false;      ||
                                          ||      cdev->updated = true;
                                          ||      // completes execution
          call thermal_cdev_update()      ||
              // cdev->updated == true    ||
              return;                     ||
                                          \/
                                          time
      
      k2 has already looped through the thermal instances looking for the deepest
      cooling device state and is preempted right before setting cdev->updated to
      true. Now, k1 runs, modifies the thermal instance state and sets cdev->updated
      to false. Then, k1 is preempted and k2 continues the execution by setting
      cdev->updated to true, therefore preventing k1 from performing the update.
      Notice that this is not an issue if k2 looks at the instance->target modified by
      k1 "after" it is assigned by k1. In fact, in this case the update will happen
      anyway and k1 can safely return immediately from thermal_cdev_update().
      
      This may lead to a situation where a thermal governor never updates the cooling
      device. For example, this is the case for the step_wise governor: when calling
      the function thermal_zone_trip_update(), the governor may always get a new state
      equal to the old one (which, however, wasn't notified to the cooling device) and
      will therefore skip the update.
      
      CC: Zhang Rui <rui.zhang@intel.com>
      CC: Eduardo Valentin <edubezval@gmail.com>
      CC: Peter Feuerer <peter@piie.net>
      Reported-by: NToby Huang <toby.huang@arm.com>
      Signed-off-by: NMichele Di Giorgio <michele.digiorgio@arm.com>
      Reviewed-by: NJavi Merino <javi.merino@arm.com>
      Signed-off-by: NZhang Rui <rui.zhang@intel.com>
      d0b7306d
  4. 28 4月, 2016 1 次提交
  5. 21 4月, 2016 1 次提交
  6. 18 3月, 2016 1 次提交
  7. 07 1月, 2016 1 次提交
  8. 29 12月, 2015 3 次提交
  9. 14 9月, 2015 1 次提交