If the goal for 2.6.20 was to be a stable release (and it was), the goal for 2.6.21 is to have just survived the big timer-related changes and some of the other surprises (just as an example: we were apparently unlucky enough to hit what looks like a previously unknown hardware errata in one of the ethernet drivers that got updated etc).
So it's been over two and a half months, and while it's certainly not the
longest release cycle ever, it still dragged out a bit longer than I'd
have hoped for and it should have. As usual, I'd like to thank Adrian (and
the people who jumped on the entries Adrian had) for keeping everybody on
their toes with the regression list - there's a few entries there still,
but it got to the point where we didn't even know if they were real
regressions, and delaying things further just wasn't going to help.
So the big change during 2.6.21 is all the timer changes to support a
tickless system (and even with ticks, more varied time sources). Thanks
(when it no longer broke for lots of people ;) go to Thomas Gleixner and
Ingo Molnar and a cadre of testers and coders.
Of course, the timer stuff was just the most painful and core part (and
thus the one that I remember most): there's a lot of changes all over. The
appended changelog is just for the fixes since -rc7, so that doesn't look
very impressive, the full changes since 2.6.20 are obviously a *lot*
bigger (and you're better off reading the individual -rc changelogs).
We now return you to your regular scheduler discussions,
Linus
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