On Sun, Mar 06, 2022 at 07:51:42PM +0900, Byungchul Park wrote: > > > > Users of DEPT must not have to understand how DEPT works in order to > > Users must not have to understand how Dept works for sure, and haters > must not blame things based on what they guess wrong. For the record, I don't hate DEPT. I *fear* that DEPT will result in my getting spammed with a huge number of false posiives once automated testing systems like Syzkaller, zero-day test robot, etcs., get a hold of it once it gets merged and start generating hundreds of automated reports. And when I tried to read the DEPT reports, and the DEPT documentation, and I found that its explanation for why ext4 had a circular dependency simply did not make sense. If my struggles to understand why DEPT was issuing a false positive is "guessing", then how do we have discussions over how to make DEPT better? > > called prepare-to-wait on more than one wait queue, how is DEPT going > > to distinguish between your "morally correct" wkaeup source, and the > > "rescue wakeup source"? > > Sure, it should be done manually. I should do it on my own when that > kind of issue arises. The question here is how often will it need to be done, and how easy will it be to "do it manually"? Suppose we mark all of the DEPT false positives before it gets merged? How easy will it be able to suppress future false positives in the future, as the kernel evolves? Perhaps one method is to haved a way to take a particular wait queue, or call to schedule(), or at the level of an entire kernel source file, and opt it out from DEPT analysis? That way, if DEPT gets merged, and a maintainer starts getting spammed by bogus (or incomprehensible) reports, there is a simople way they can annotate their source code to prevent DEPT from analyzing code that it is apparently not able to understand correctly. That way we don't necessarily need to have a debate over how close to zero percent false positives is necessary before DEPT can get merged. And we avoid needing to force maintainers to prove that a DEPT report is a false positive, which is from my experience hard to do, since they get accused of being DEPT haters and not understanding DEPT. - Ted
