Train your team

KRN-232 · Linux Kernel Core

Memory Barriers & the Kernel Memory Model

The hardest correctness topic in the kernel: reordering, barriers, and reasoning about concurrent code that actually holds.

Expert 3 days in person6 half-days online Max 14 in person

Who this course is for

Senior kernel, driver and runtime engineers writing or reviewing lockless code — the people whose bugs only reproduce on other people's hardware.

Prerequisites

KRN-230 and KRN-231 or equivalent concurrency depthSolid CAbility to skim disassembly

Course outline

Day 1 — Reordering is real

  • Compiler reordering vs CPU reordering, and why both matter
  • Store buffers and invalidate queues: the hardware intuition
  • smp_mb, smp_rmb, smp_wmb and what each forbids
  • Acquire and release semantics as the modern default
  • READ_ONCE and WRITE_ONCE: what they do and do not do

Day 2 — The Linux Kernel Memory Model

  • What the LKMM formalises and why it exists
  • Litmus tests: structure, naming and how to read an outcome
  • Running litmus tests with herd7
  • The classic patterns: message passing, load buffering, store buffering
  • Mapping model outcomes back to real architectures

Day 3 — Dependencies and review

  • Address, data and control dependencies
  • The traps inside control dependencies specifically
  • Reviewing lockless code without fooling yourself: a structured checklist
  • When to give up and take the lock
  • Capstone workshop

Hands-on labs

Labs follow the academy model — 35% principles, 20% guided investigation, 45% engineering studio. Every claim you make in a lab is backed by a trace, a counter or a measurement you captured yourself. How we teach

  1. Lab: run classic litmus patterns (MP, LB, SB) through herd7 and predict each outcome before the tool confirms it
  2. Lab: break a message-passing handoff by removing a barrier and observe the failure — or explain why your architecture hides it
  3. Lab: audit a real kernel lockless path against LKMM rules and document every ordering guarantee
  4. Lab: rewrite a racy lockless sequence with acquire/release and verify it with KCSAN
  5. Lab: construct a control-dependency bug and explain precisely why it miscompiles

Capstone project

Review a piece of lockless kernel code the way a maintainer would: an ordering argument for every shared access, herd7 litmus tests for the two riskiest patterns, KCSAN evidence, and a final verdict — merge, fix, or take the lock — with reasoning that survives hostile review.

What you leave with

  • A working command of the Linux Kernel Memory Model
  • Litmus testing with herd7
  • Precise use of acquire/release and READ_ONCE/WRITE_ONCE
  • A review checklist for lockless code you can apply on Monday

How it runs

Every course follows the same model: 35% principles, 20% guided investigation, 45% engineering studio. You leave with working code, raw measurements and an evidence-based report — not a certificate of attendance. Read the methodology or see a full sample lesson.

Material is adapted to your kernel version, hardware and workload before a private delivery. For public cohorts, the environment is provided and configured.

Questions

Who is this course for?

Senior kernel, driver and runtime engineers writing or reviewing lockless code — the people whose bugs only reproduce on other people's hardware. It sits at expert level within the Linux Kernel Core track.

What do I need to know already?

Specific prerequisites for this course: KRN-230 and KRN-231 or equivalent concurrency depth; Solid C; Ability to skim disassembly. We confirm levels before the cohort starts and adapt if a group is stronger or weaker than expected.

Can this run privately for my team?

Yes. Any course runs on-site at your offices anywhere, or live online for a distributed team, with labs adapted to your hardware and codebase.

What is the difference between in-person and online?

In person is 3 full days with hardware on your desk, capped at 14. Online is 6 half-day sessions across about two weeks so you can keep working, capped at 20, with remote lab access.

Do you invoice companies?

Yes. Purchase orders are accepted and invoicing is available in USD, EUR, GBP, SAR and CAD.

Upcoming dates

DatesWhereSeatsEarly birdRegular
8 Nov – 10 Nov 20263 full days RiyadhIn person · KAFD Conference Centre 8 of 14 SAR 9,110until 9 OctSAR 10,120
15 Nov – 17 Nov 20263 full days Kuwait CityIn person · Al Hamra Tower 3 of 14 KWD 760until 16 OctKWD 840
15 Nov – 17 Nov 20263 full days MuscatIn person · Knowledge Oasis Muscat 8 of 14 OMR 940until 16 OctOMR 1,040
22 Nov – 29 Nov 20266 half-days Gulf bandLive online · 09:00–13:00 GMT+3 14 of 20 US$1,760until 23 OctUS$1,950
23 Nov – 25 Nov 20263 full days OttawaIn person · Kanata North Tech Park 3 of 14 CAD 3,300until 24 OctCAD 3,670
23 Nov – 30 Nov 20266 half-days Europe bandLive online · 09:00–13:00 CET 3 of 20 US$1,760until 24 OctUS$1,950
30 Nov – 2 Dec 20263 full days TorontoIn person · MaRS Discovery District 8 of 14 CAD 3,300until 31 OctCAD 3,670
30 Nov – 2 Dec 20263 full days LondonIn person · Shoreditch Works 3 of 14 GBP 1,900until 31 OctGBP 2,110
30 Nov – 7 Dec 20266 half-days Americas bandLive online · 13:00–17:00 ET 8 of 20 US$1,760until 31 OctUS$1,950
7 Dec – 9 Dec 20263 full days BerlinIn person · Factory Görlitzer Park 8 of 14 EUR 2,230until 7 NovEUR 2,480

Dates shown for the next few months. If nothing fits, tell us where and when — cohorts are added on demand, and private delivery can be scheduled any week.

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