On 31/08/16 11:23, Pavel Andrianov wrote: > 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. Good find. Will need reordering to set the ok_to_ignore_lock first. Whether it ever actually happens will depend on just how long that EOC interrupt takes to happen. Still it's a theoretical problem with a fairly simple fix so let's fix it. > > 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. > Agreed - looks like some reordering is needed here as well.
Jonathan
