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