openentropy_core/sources/scheduling/
thread_lifecycle.rs

1//! Thread lifecycle timing — entropy from pthread create/join scheduling.
2
3use std::thread;
4
5use crate::source::{EntropySource, Platform, SourceCategory, SourceInfo};
6use crate::sources::helpers::{extract_timing_entropy, mach_time};
7
8/// Harvests timing jitter from thread creation and destruction.
9///
10/// # What it measures
11/// Nanosecond timing of the full `pthread_create` + `pthread_join` cycle,
12/// with variable per-thread workloads.
13///
14/// # Why it's entropic
15/// Each thread lifecycle exercises deep kernel scheduling paths:
16/// - **Mach thread port allocation** from the kernel IPC port name space
17/// - **Zone allocator** allocation for the kernel thread structure
18/// - **CPU core selection** — P-core vs E-core, influenced by ALL threads
19/// - **Stack page allocation** via `vm_allocate`
20/// - **TLS setup** including dyld per-thread state
21/// - **Context switch on join** — depends on current runqueue state
22/// - **Core migration** — new thread may run on a different core
23///
24/// # What makes it unique
25/// Thread lifecycle timing is a previously untapped entropy source. The
26/// combination of kernel memory allocation, scheduling decisions, and
27/// cross-core communication produces 89 unique LSB values — the richest
28/// of any frontier source.
29///
30/// # Configuration
31/// No configuration needed — this source has no tunable parameters.
32pub struct ThreadLifecycleSource;
33
34static THREAD_LIFECYCLE_INFO: SourceInfo = SourceInfo {
35    name: "thread_lifecycle",
36    description: "Thread create/join kernel scheduling and allocation jitter",
37    physics: "Creates and immediately joins threads, measuring the full lifecycle timing. \
38              Each cycle involves: Mach thread port allocation, zone allocator allocation, \
39              CPU core selection (P-core vs E-core), stack page allocation, TLS setup, and \
40              context switch on join. The scheduler\u{2019}s core selection depends on thermal \
41              state, load from ALL processes, and QoS priorities.",
42    category: SourceCategory::Scheduling,
43    platform: Platform::Any,
44    requirements: &[],
45    entropy_rate_estimate: 2.0,
46    composite: false,
47    is_fast: false,
48};
49
50impl EntropySource for ThreadLifecycleSource {
51    fn info(&self) -> &SourceInfo {
52        &THREAD_LIFECYCLE_INFO
53    }
54
55    fn is_available(&self) -> bool {
56        true
57    }
58
59    fn collect(&self, n_samples: usize) -> Vec<u8> {
60        let raw_count = n_samples * 4 + 64;
61        let mut timings: Vec<u64> = Vec::with_capacity(raw_count);
62        let mut lcg: u64 = mach_time() | 1;
63
64        for _ in 0..raw_count {
65            lcg = lcg.wrapping_mul(6364136223846793005).wrapping_add(1);
66            let work_amount = (lcg >> 48) as u32 % 100;
67
68            let t0 = mach_time();
69            let handle = thread::spawn(move || {
70                let mut sink: u64 = 0;
71                for j in 0..work_amount {
72                    sink = sink.wrapping_add(j as u64);
73                }
74                std::hint::black_box(sink);
75            });
76            let _ = handle.join();
77            let t1 = mach_time();
78            timings.push(t1.wrapping_sub(t0));
79        }
80
81        extract_timing_entropy(&timings, n_samples)
82    }
83}
84
85#[cfg(test)]
86mod tests {
87    use super::*;
88
89    #[test]
90    fn info() {
91        let src = ThreadLifecycleSource;
92        assert_eq!(src.name(), "thread_lifecycle");
93        assert_eq!(src.info().category, SourceCategory::Scheduling);
94        assert!(!src.info().composite);
95    }
96
97    #[test]
98    #[ignore] // Spawns threads
99    fn collects_bytes() {
100        let src = ThreadLifecycleSource;
101        assert!(src.is_available());
102        let data = src.collect(64);
103        assert!(!data.is_empty());
104        assert!(data.len() <= 64);
105        if data.len() > 1 {
106            let first = data[0];
107            assert!(data.iter().any(|&b| b != first), "all bytes identical");
108        }
109    }
110}
openentropy_core/sources/scheduling/thread_lifecycle.rs

openentropy_core/sources/scheduling/
thread_lifecycle.rs
