ABI mutation (was New kernels and old distributions) [LWN.net]

ABI mutation (was New kernels and old distributions)

Posted Aug 3, 2006 14:34 UTC (Thu) by davecb (subscriber, #1574)
In reply to: ABI mutation (was New kernels and old distributions) by AnswerGuy
Parent article: New kernels and old distributions

I quite understand: I said I was brutally oversimplifying (;-)). Paul Stachour had an hour-long lecture on the subject, and that just touched on the easy examples, in structs and RDBMSs.

In practice, the consumer only has a finite period in which to adopt the new version of the interface, which was reportedly only two change cycles, and only incompatable changes, such as completely rewriting the structures used caused a forced change.

At that point, one was saying exactly that: all of you have to fix this! The advantage is that they didn't have to fix it on your schedule. Instead they fixed it on theirs. If they didn't want to fix it, of course, they could always go out of business (;-))

This ability to schedule disparate teams was the big value-add: you didn't have to convince everyone in the world to ship a patch next Tuesday.

Compatible changes, like adding a field to the end (normal practice), were commonly ignored by consumers who didn't use the field, but consumers who did could get it added without forcing all the other consumers to change. That was the common case, by the way: I'd ask Edsel for something for one consumer, he'd add it, my code would start using it and the other consumers wouldn't care.

Finally, I quite agree that there should be a corpus of kernel coupled sources, maintained either by the kernel community or, in the case of some hardware, by teams funded by those vendors. The latter practice is visible in the Samba team, where committed users of the software have staff working in or with the core team.

--davecb@spamcop.net

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