From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [1/6] 2.6.21-rc2: known regressions
Date: Sun, 4 Mar 2007 18:26:19 -0800
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	<20070305015031.GF3441@stusta.de>
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Cc: Ayaz Abdulla <aabdulla@nvidia.com>, Pavel Machek <pavel@ucw.cz>,
   Garzik <jeff@garzik.org>, Jeff@smtp.osdl.org,
   Marcel Holtmann <marcel@holtmann.org>, Matt Mackall <mpm@selenic.com>,
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   Linus Torvalds <torvalds@linux-foundation.org>,
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To: Adrian Bunk <bunk@stusta.de>
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On Mon, 5 Mar 2007 02:50:31 +0100 Adrian Bunk <bunk@stusta.de> wrote:

> This email lists some known regressions in 2.6.21-rc2 compared to 2.6.20
> that are not yet fixed in Linus' tree.


We seem to have broken an unusually large amount of stuff this time.

partial post-mortem:

- The ACPICA merge landed in -mm super-late: basically it was in mainline
  a week afterwards and saw only a single -mm release.

  Part of the reason for this short period in -mm was that ACPICA had its
  paws all over x86_64 code and conflicted badly with significant changes
  in the x86_64 tree.

  That happens sometimes.  But when it does, the mess lands in my lap
  rather than in the laps of the perpetrators.

  Lesson: keep the code well-factored so that different subsystems don't
  soil each others' kennels.

- The hrtimers/dynticks stuff is simply hard: timekeeping, low-level x86,
  even APICs.  These are areas in which things break a lot, so churning it
  was inevitably going to cause problems.

  Lesson: none, I think.  Low-level x86 support is just hard, and
  changing it breaks things.


So that accounts for _some_ of the damage, but I wonder if there's more to
it than that.