Module flock 

POSIX File Locking (flock/fcntl)

Implements both whole-file locking (flock semantics) and byte-range locking (fcntl/POSIX semantics). Per-inode lock tables track ownership by PID, with deadlock detection for blocking lock requests.

• flock(): whole-file advisory locks (LOCK_SH, LOCK_EX, LOCK_UN)
• fcntl_setlk(): byte-range locks (F_SETLK semantics, non-blocking)
• fcntl_setlkw(): byte-range locks (F_SETLKW semantics, blocking with deadlock detection)
• fcntl_getlk(): query conflicting locks (F_GETLK)
• cleanup_process_locks(): release all locks held by a process on exit

Structs

FileLock

A POSIX byte-range lock (used by fcntl F_SETLK / F_GETLK).

FlockEntry

A whole-file advisory lock entry (flock semantics).

Constants

F_RDLCK

Read (shared) lock

F_UNLCK

Unlock

F_WRLCK

Write (exclusive) lock

LOCK_EX

Exclusive (write) lock

LOCK_NB

Non-blocking flag (OR with LOCK_SH or LOCK_EX)

LOCK_SH

Shared (read) lock

LOCK_UN

Unlock

Functions

cleanup_process_locks

Remove all locks (flock and range) held by the specified PID.

fcntl_getlk

Query for a conflicting lock (F_GETLK semantics).

fcntl_setlk

Set a byte-range lock (F_SETLK semantics – non-blocking).

fcntl_setlkw

Set a byte-range lock with blocking (F_SETLKW semantics).

flock

Apply a whole-file advisory lock (flock semantics).