Module memory 

Memory management for daemon processes.

DT-007: Swap Deadlock Prevention

This module provides memory locking functionality to prevent swap deadlock for daemons that serve as swap devices (e.g., trueno-ublk).

The Problem

When a daemon serves as a swap device, a deadlock can occur:

1. Kernel needs to swap pages OUT to the daemon’s device
2. Daemon needs memory to process I/O request
3. Kernel tries to swap out daemon’s pages to free memory
4. Swap goes to the same daemon → waiting for itself → DEADLOCK

Evidence

Kernel log from 2026-01-06 stress test:

INFO: task trueno-ublk:59497 blocked for more than 122 seconds.
task:trueno-ublk state:D (uninterruptible sleep)
__swap_writepage+0x111/0x1a0
swap_writepage+0x5f/0xe0

Solution

Use mlockall(MCL_CURRENT | MCL_FUTURE) to pin all daemon memory, preventing the daemon itself from being swapped out.

Enums

MlockResult

Result of memory locking operation.

Functions

apply_memory_config

Apply memory-related resource configuration.

is_memory_locked

Check if memory is currently locked.

lock_daemon_memory

Lock all current and future memory allocations to prevent swapping.

unlock_daemon_memory

Unlock all memory (for cleanup/testing).