[BUG] iio: light: opt3001: possible deadlock in opt3001_read_raw() and opt3001_irq()

[Jia-Ju Bai]

Hello,

My static analysis tool reports a possible deadlock in the opt3001 
driver in Linux 5.16:

opt3001_read_raw()
  mutex_lock(&opt->lock); --> Line 399 (Lock A)
  opt3001_get_lux()
    wait_event_timeout(opt->result_ready_queue, ...) --> Line 276 (Wait X)
  mutex_lock(&opt->lock); --> Line 412 (Unlock A)

opt3001_irq()
  mutex_lock(&opt->lock); --> Line 693 (Lock A)
  mutex_unlock(&opt->lock); --> Line 730 (Unlock A)
  wake_up(&opt->result_ready_queue); --> Line 733 (Wake X)

When opt3001_read_raw() is executed, "Wait X" is performed by holding 
"Lock A". If opt3001_irq() is executed at this time, "Wake X" cannot be 
performed to wake up "Wait X" in opt3001_read_raw(), because "Lock A" 
has been already hold by opt3001_read_raw(), causing a possible deadlock.
I find that "Wait X" is performed with a timeout, to relieve the 
possible deadlock; but I think this timeout can cause inefficient execution.

I am not quite sure whether this possible problem is real and how to fix 
it if it is real.
Any feedback would be appreciated, thanks :)


Best wishes,
Jia-Ju Bai