Cancel Test

• This is interesting.
  • Three threads. Basic-test infinite loop +
  • Wacko cancel thread
• This is big.
  • 4 GB of state; 10 million states; at least 100000 maxdepth
• This found a real bug
  • On uniprocessor, with cooperative scheduling, another thread runs only if current thread blocks
  • Means threads are never canceled while running
  • If cancel check before blocking succeeds, a mutex isn’t unlocked. (In cond_wait())