A potential bug in drivers/iio/light/opt3001.ko

[Pavel Andrianov]

Hi!

There is a bug in drivers/iio/light/opt3001.ko. Regard such case:

Thread 1                             Thread 2
-> opt3001_read_raw
  -> mutex_lock(&opt->lock)
  -> opt3001_get_lux()
    ..
    ->i2c_smbus_write_word_swapped()
            Now an interrupt comes
                                     -> opt3001_irq
                                       -> mutex_lock(&opt->lock)

This is a deadlock, as the flag ok_to_ignore_lock has not been set yet.

Regard another case:

Thread 1                             Thread 2
-> opt3001_read_raw
  -> mutex_lock(&opt->lock)
  -> opt3001_get_lux()
    ..
    -> i2c_smbus_write_word_swapped()
    opt->ok_to_ignore_lock = true;
            Now an interrupt comes
                                     -> opt3001_irq
                                       ..
                                       opt->result_ready = true
                                       wake_up()
     opt->result_ready = false;
     wait_event_timeout()

In this case the first thread misses the result and waits until timeout 
expires.

--
Pavel Andrianov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: andrianov@xxxxxxxxx