On 05/09/16 15:15, Pavel Andrianov wrote: > 03.09.2016 19:38, Jonathan Cameron пишет: >> 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 >> > > In opt3001_get_lux has a comment, that i2c_smbus_write_word_swapped > (line 246) enables interrupt mechanism. If an interrupt can not arise > before the function, the assignments to both of flags should be moved > before i2c_smbus_write_word_swapped and this is the best fix for both > of issues. Do you know if my assumption is correct and interrupts are > disabled before i2c_smbus_write_word_swapped call? Andreas, can you confirm this for us? Thanks, Jonathan -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
