KernelTrap - Linus Torvalds

Linux: 2.6.34-rc4, "Hunting A Really Annoying VM Regression"

Jeremy — Tue, 13 Apr 2010 05:16:30 +0000

"It's been two weeks rather than the usual one, because we've been hunting a really annoying VM regression that not a lot of people seem to have seen, but I didn't want to release an -rc4 with it," began Linux creator Linus Torvalds, announcing the 2.6.34-rc4 Linux kernel. He explained, "we had the choice of either reverting all the anon-vma scalability improvements, or finding out exactly what caused the regression and fixing it. And we got pretty close to the point where I was going to just revert it all." Linus continued:

"Absolutely _huge_ kudos to Borislav Petkov who reported the problem and was able to not just reliably reproduce it, but also test new patches to try to narrow things down at a moments notice. The thing took ten days of emails flying back and forth, and Borislav was there all the time, day and night, through several patches that tried to fix it (several real bugs, but not the one he hit) and lots of patches to just add instrumentation to get us nearer to the cause of the problem. And finally, today, confirmation that we actually nailed the problem. So if anybody has been seeing a oops (or sometimes a GP fault) in page_referenced(), that should be gone now."

As for the rest of the changes, Linus noted, "the bulk of the changes come from drivers - a new network driver (cxgb4), but also updates to the radeon and nouveau drivers. And then there is the random updates everywhere." Read on for the full changelog.

Quote: The Real Bug

Jeremy — Tue, 30 Sep 2008 15:38:36 +0000

"The _real_ bug is clearly in the hardware design that allows you to brick those things without apparently even having a lock bit. I'm hoping Intel doesn't treat this as just a software bug. Some hw designer should be thinking hard about which orifice they put their head up in."

2.6.27-rc6, "Things Are Calming Down"

Jeremy — Fri, 12 Sep 2008 22:42:58 +0000

"The patches most people hopefully care about tend to be small details," noted Linus Torvalds, announcing the 2.6.27-rc6 kernel. He continued, "and so more regressions should hopefully be closed now, some by just reverting the commits that caused breakage. I don't think anything special merits explicit comment, but you can get a flavor for things by scanning the appended shortlog." Earlier in the announcement email, Linus did note some specifics about which drivers caused the bulk of the patch:

"Same old deal - except it's been almost two weeks since -rc5. That said, the diff is actually about the same size, so I guess that means things are calming down. Most of the diff (bulk-wise) is updates to the new gspca (standard USB webcam) driver, although some of it is also removal of the dead miropcm20* driver."

2.6.27-rc5, Fixing Regressions

Jeremy — Mon, 01 Sep 2008 14:48:03 +0000

Linus Torvalds announced the 2.6.27-rc5 Linux Kernel, noting that his "weekly releases" tend to happen every eight days, adding, "the bulk of it is all config updates, and with arm and powerpc leading the pack." Linus continued:

"While the config updates amount to about three quarters of the diff, and if you don't use a rename-aware diff the blackfin include file movement pretty much accounts for the rest, hidden behind all those trivial (but bulky) changes are a lot of small changes that hopefully fix a number of regressions.

"The most exciting (well, for me personally - my life is apparently too boring for words) was how we had some stack overflows that totally corrupted some basic thread data structures. That's exciting because we haven't had those in a long time. The cause turned out to be a somewhat overly optimistic increase in the maximum NR_CPUS value, but it also caused some introspection about our stack usage in general. Including things like a patch to gcc to fix insane stack usage for vararg functions on x86-64. But that one would only hit anybody who was a bit too adventurous and selected the big 4096 CPU configuration. The rest of the regressions fixed are a bit more pedestrian."

2.6.27-rc4, "Random Stuff All Over"

Jeremy — Mon, 25 Aug 2008 21:10:02 +0000

"Another week, another -rc," began Linus Torvalds, announcing the 2.6.27-rc4 Linux kernel, continuing, "this time the diffstat is almost totally dominated by the addition of the musb driver that drives the MUSB and TUSB controllers integrated into omap2430 and davinci. That, together with the removal of the auerswald USB driver (replaced by libusb version) is more than half of the bulk of the patch, and obviously most users won't ever notice." Linus added:

"Apart from those bulky USB updates, there's some arch updates (blackfin and ia64), network and input driver updates, and an XFS and UBIFS update. The rest is mostly random stuff all over, probably best described by the appended shortlog. A number of regressions should be off the table, but more remain..."

Quote: Maybe I'm Overly Pessimistic

Jeremy — Fri, 22 Aug 2008 02:53:07 +0000

"The C standard will eventually support concurrency (they are working on it), and it will almost inevitably be a horrible pile of stinking sh*t, and we'll continue to use the gcc inline asms instead, but then the gcc people will ignore our complaints when they break the compiler, and say that we should use the stinking pile-of-sh*t ones that are built in.

Quote: Very Hacky Indeed

Jeremy — Tue, 19 Aug 2008 11:45:39 +0000

"The delta cache was really a huge hack that just turned out rather successful. It's been hacked on further since (to do some half-way reasonable replacement with _another_ hack by adding an LRU on top of it), but it really is very hacky indeed."

2.6.27-rc3, "Things Really _Have_ Calmed Down"

Jeremy — Wed, 13 Aug 2008 18:49:12 +0000

"Things really _have_ calmed down, and hopefully we've also resolved a lot of the regressions in -rc3," began Linus Torvalds, announcing the 2.6.27-rc3 Linux kernel. He noted that much of the patch size was from the inclusion of the new ath9k wireless driver, with much of the rest of the patch size due to the renaming of many arch include files in the ARM, AVR32 and m68lnommu architectures. Linus continued:

"All the small changes are where the regression fixes are, and other random improvements. And they're all over. The ShortLog (appended) probably gives a taste of it."

Quote: Bloat Is Bloat

Jeremy — Fri, 08 Aug 2008 18:46:32 +0000

"The default value should be 'off', unless it's _needed_ by people. Have you guys looked at the size of the kernel lately? Bloat is bloat. Just because it's conditional is not an excuse."