Hello,
My static analysis tool reports a possible deadlock in the nfp driver in
Linux 5.16:
nfp_cpp_area_acquire()
mutex_lock(&area->mutex); --> Line 455 (Lock A)
__nfp_cpp_area_acquire()
wait_event_interruptible(area->cpp->waitq, ...) --> Line 427 (Wait X)
nfp_cpp_area_release()
mutex_lock(&area->mutex); --> Line 502 (Lock A)
wake_up_interruptible_all(&area->cpp->waitq); --> Line 508 (Wake X)
When nfp_cpp_area_acquire() is executed, "Wait X" is performed by
holding "Lock A". If nfp_cpp_area_release() is executed at this time,
"Wake X" cannot be performed to wake up "Wait X" in
nfp_cpp_area_acquire(), because "Lock A" has been already hold by
nfp_cpp_area_acquire(), causing a possible deadlock.
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