Developers split over split-lock detection

Posted Dec 9, 2019 12:07 UTC (Mon) by cesarb (subscriber, #6266)
In reply to: Developers split over split-lock detection by marcH
Parent article: Developers split over split-lock detection

The logic behind that statement is: (1) most people use the defaults; (2) there's no pressure on fixing the bug if most people aren't affected, especially if those few people affected are using a non-default setting which can be turned off without visibly breaking anything else.

That is, in the scenario where this feature is default-enabled, broken software will end up being fixed; in the scenario where this feature is default-disabled, not only will broken software not be fixed (there being no pressure to do so), but also there will be pressure to never enable this feature.

Personally, I think this feature should be enabled by default, since it's a security fix against a local DoS issue, with a compatibility knob for those running systems with trusted but buggy software.

Developers split over split-lock detection

Posted Dec 9, 2019 16:34 UTC (Mon) by marcH (subscriber, #57642) [Link]

> The logic behind that statement is: (1) most people use the defaults

Why write "everyone" if/when you mean "most"? Considering the main question is "how many?", it gives the impression that one hasn't really thought about it.

There are cases where the difference between "all" and "most" doesn't matter. But here it does because it takes very few early adopters to find bugs. Even fewer if they're running a data center.

> (2) there's no pressure on fixing the bug if most people aren't affected, [...] not only will broken software not be fixed (there being no pressure to do so), but also there will be pressure to never enable this feature.

How's any of that worse than not merging the code at all?

Is blocking the code itself merely used as leverage in the discussion about the default setting?

Developers split over split-lock detection

Posted Dec 9, 2019 23:46 UTC (Mon) by nix (subscriber, #2304) [Link] (1 responses)

> Personally, I think this feature should be enabled by default, since it's a security fix against a local DoS issue, with a compatibility knob for those running systems with trusted but buggy software.

Isn't a SIGBUS also a local DoS? Rather more of one than a 1000-clock stall?

Developers split over split-lock detection

Posted Dec 9, 2019 23:50 UTC (Mon) by corbet (editor, #1) [Link]

The signal only affects the process creating the split lock. The slowdown affects the entire system...