Paul E. McKenney (paulmck) wrote,
Paul E. McKenney
paulmck

Stupid RCU Tricks: A tour through rcutorture

Although Linux-kernel RCU gets most of the attention, without rcutorture, RCU would not be what it is today. To see this, note that the old saying “If it ain't tested, it don't work!” is if anything more valid today than it was back then. After all, software has not gotten any simpler, workloads have not become less demanding, and systems have not grown smaller, except in terms of physical size. That said, the decrease in size has been truly impressive. Back when Jack and I invented RCU, the hardware contained in my laptop would have filled no fewer than fifteen standard racks, and that ignores the hardware that simply was not available back then, and also ignores the reliability issues that would have resulted from such an imposing agglomeration of hardware.

It is rcutorture's job to make sure that Linux-kernel RCU actually works, and so it is worthwhile getting to know rcutorture a bit better. The following blog posts cover design of, use of, and experience with this test suite:

  1. Stupid RCU Tricks: So you want to torture RCU? (use)
  2. Stupid RCU Tricks: So rcutorture is Not Aggressive Enough For You? (use)
  3. Stupid RCU Tricks: Failure Probability and CPU Count (use)
  4. Stupid RCU Tricks: Enlisting the Aid of a Debugger (use)
  5. Stupid RCU Tricks: Torturing RCU Fundamentally, Part I (design)
  6. Stupid RCU Tricks: Torturing RCU Fundamentally, Part II (design)
  7. Stupid RCU Tricks: Torturing RCU Fundamentally, Part III (design)
  8. Stupid RCU Tricks: Torturing RCU Fundamentally, Parts IV and V (design)
  9. Stupid RCU Tricks: So rcutorture is Still Not Aggressive Enough For You? (use)
  10. Stupid RCU Tricks: rcutorture fails to find an RCU bug (experience)
  11. Stupid RCU Tricks: The design of rcutorture (design)
  12. Stupid RCU Tricks: Which tests do I run??? (use)
  13. Stupid RCU Tricks: Making Race Conditions More Probable (design)
  14. Stupid RCU Tricks: Creating Branches For the -rcu Tree (git)
  15. Stupid RCU Tricks: So You Want To Add Kernel-Boot Parameters Behind rcutorture's Back? (use)
  16. Stupid RCU Tricks: So You Want to Torture RCU With a Non-Trivial Userspace? (use)

And here are a few older posts covering rcutorture:

  1. Hunting Heisenbugs (experience, 2009)
  2. Hunting More Heisenbugs (experience, 2009)
  3. Stupid RCU Tricks: RCU Priority Inversion (design, 2010)
  4. And it used to be so simple... (design, 2011)
  5. Stupid RCU Tricks: Bug Found by Refactored Tests (design, experience, and use, 2014)
  6. Stupid RCU Tricks: rcutorture Catches an RCU Bug (experience, 2014)
  7. Stupid RCU Tricks: rcutorture Accidentally Catches an RCU Bug (experience, 2017)
Ah, but what about formal verification? But of course! Please see this series, and especially this post.

I hope that this series is helpful, and I further hope that it will inspire more aggressive torturing of other software!
Tags: rcu, rcutorture, scalability, stupid rcu tricks
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