Hello.

While searching for races in the Linux kernel I've come across "drivers/misc/apds990x.ko" module. Here are questions that I came up with while analyzing results. Lines are given using the info from Linux v4.12.


Consider the following case:

Thread 1:                      Thread 2:
apds990x_suspend
apds990x_resume                apds990x_irq
-> apds990x_chip_on              if (!pm_runtime_suspended
                                                  (chip->client->dev)){
   -> apds990x_configure           if (status & APDS990X_ST_AINT) {
        chip->again_meas = 1         chip->again_meas = chip->again_next
        (apds990x.c: line 571)       (apds990x.c: line 505)
                                   }
                                  }

First question. Is this race feasible from your point of view?
Second question. The check for the device suspension status (pm_runtime_suspended()) is present in the interrupt handler, but the functions pm_runtime_set_suspended / pm_runtime_set_active are not used in apds990x_suspend / apds990x_resume respectively. Do you know about any other method being used to make the modification of suspension status?

Thank you for your time.

-- Anton Volkov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: avol...@ispras.ru

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