Oops, meant to send to linux-kernel instead of linux-man. Please ignore. ~Theodore > On Jan 30, 2019, at 7:31 PM, Theodore Dubois <tblodt@xxxxxxxxxx> wrote: > > I'm having trouble figuring out how the kernel handles a particular case in deadlock detection on posix file locks. Here's the scenario: > > PID 1: locks byte 2 > PID 3: locks byte 0 > PID 2: locks byte 10 > PID 1: locks byte 10 > PID 2: locks bytes 0-2 inclusive > > The last step fails with EDEADLK, but I'm not sure how that is detected. The specified range conflicts with two different locks, and the first loop in posix_lock_inode would find whichever one comes first in the linked list, and pass that to the deadlock detector. > > If the lock on byte 2 comes first in the list, a cycle would be found between the lock on byte 2 and the lock on byte 10. But if the lock on byte 0 comes first, the deadlock detector would return NULL from what_owner_is_waiting_for on that lock since PID 3 has no other locks, and immediately succeed. > > What am I missing? > > Thanks, > ~Theodore >
