Question about apds990x.ko

From: Anton Volkov
Date: Thu Aug 10 2017 - 10:57:38 EST


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: avolkov@xxxxxxxxx