* edge case posix file lock deadlock detection
@ 2019-01-31 3:31 Theodore Dubois
0 siblings, 0 replies; only message in thread
From: Theodore Dubois @ 2019-01-31 3:31 UTC (permalink / raw)
To: Theodore Dubois; +Cc: linux-man, kernelnewbies
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
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2019-01-31 3:31 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-01-31 3:31 edge case posix file lock deadlock detection Theodore Dubois
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).