/srv/irclogs.ubuntu.com/2013/09/19/#ubuntu-kernel.txt

ppisatiHello world! :)05:48
* apw yawns at the world07:29
ppisatiapw: goodmorning sweetheart :)07:49
apwppisati, morning my lovely07:49
ppisati:)07:50
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ppisatiweren't dtb supposed to be treated like a stable ABI? weren't old dtb supposed to be supported by newer kernels?!?!?08:58
ppisatibah, it boots at least...09:01
apwppisati, heh ... yeah right09:53
ppisatiapw: besides, the answer is no: http://lwn.net/Articles/560523/10:01
apwppisati, so the answer is yes they should, but not they don't cause we are crap at it10:04
ppisatiapw: right, so to be on the safe side, always update kernel and dtb together, else your board could stop booting10:04
apwas the dts comes with the kernle in the main, that isn't so difficult, but it really really shouldn't10:05
ppisatiapw: well, problem is that on some platform the dtb is buried in the firmware so, everytime you install a new kernel, you *should* reflash the firmware10:16
ppisatiapw: but this time around, i just lost one day on my new bone, because the dtb that came with a 3.8 kernel10:16
apwppisati, sign10:16
apwppisati, sigh10:16
ppisatiapw: hanged 3.11 and i spent the entire yesterday debugging it 10:16
apwwhat a royal pain in the ass, and something we need to socialise that there are real risks in upgrading10:17
ppisatiapw: and when i woke this morning i thought "well, what if it's the dtb?!?!?"10:17
apwppisati, that is the "shower brain" in action10:17
ppisatiapw: and that's it, now it kind of boot10:17
ppisatiright10:17
ppisatiit took me, one day to learn that the serial cable (a usb with an embedded ftdi chip) doesn't work if connected to a usb cable extension10:18
ppisatianother one to find out that the board provided dtb doesn't work with recent kernel10:19
ppisatiand now let's see...10:19
apwppisati, a struggle indeed10:41
ppisatiapw: well, not really, it's just that i loose way too much time on stupid details...10:43
ppisatiapw: anyhow, it's gym time! :)10:44
ppisatisee u later10:44
elmoSep 17 22:47:01 juju-prodstack-pes-r2-instance-1 kernel: [17844307.966142] INFO: rcu_sched detected stall on CPU 3 (t=1078390 jiffies)11:07
elmoSep 17 22:47:01 juju-prodstack-pes-r2-instance-1 kernel: [17844307.967042] sending NMI to all CPUs:11:07
elmo^-- does that interrupt userland 11:07
elmoerr11:07
elmo^-- does that interrupt system calls at all?  e.g. could it interrupt an fsync()?11:08
apwelmo, i would not expect that to affect userland at all indeed, i would expect that to make all CPUs to service the NMI and continue where they left off11:54
elmoapw: cool, thanks11:57
ChickenCutlassapw, hi there,  I want to build a custom kernel in my PPA.  But everytime I bump the changelog and build a source pakcage, it blows away my changelog entry.13:10
ChickenCutlassapw, what is the correct way to do this?13:10
apwChickenCutlass, you need to change the changelog in debian.<branch>/changelog not debian/changelog13:11
ChickenCutlassapw, ah13:11
ChickenCutlassapw, one more question.13:12
ChickenCutlassapw, I have a new MacBook Air 6,2.  The haswell one13:12
ChickenCutlassapw, and after applying 2 patches -- acpi and sound work13:12
ChickenCutlassapw, can we get those into saucy?13:12
ChickenCutlasswhat is the policy there13:13
apwChickenCutlass, its cirtainly possible, if they fix a bug, get them up on kernel-team@ with why they are needed13:13
ChickenCutlassapw, ack13:14
ckingand the provenance 13:17
ChickenCutlasscking, right.13:18
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ppisatiinfinity: ping14:19
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infinityppisati: To be fair, the dtb/kernel dependencies are something that we're desperately trying to socialize as unnecessary and fix.  So, for the short term, we might want to upgrade in lockstep, but I disagree that we want to pass that knowledge on to end users, as it will become cargo-cult misinformation.15:04
ppisatiinfinity: well, the problem is not that we want or not, if the kernel requires a new dtb, you better deliver it or be ready to debug your boot15:06
ppisatiinfinity: anyhow, i pinged you about the flash-kernel patch15:06
ppisatiinfinity: can you give it a look?15:07
infinityppisati: Right, but if the kernel requires a new DTB, it's because the previous one was broken.  Ultimately, they should be (and will be) decoupled.15:07
infinityppisati: I'll give the patch a look this morning.15:07
ppisatiinfinity: that was the promise, but it doesn't work like that15:07
infinityppisati: No, no.  I know it doesn't work like that today, I'm talking about what the future is meant to look like, however.  And socializing "you'll need to pay attention or fix this" to end users sets up a bad expectation.  We should JFDI silently where we can, and in cases where vendors actually SHIP a firmware dtb that breaks with their newer kernels honestly, that's their fault.15:13
ppisatiinfinity: agreed15:15
apwppisati, infinity, it is not obvious one can even change the thing when it is in the firmware15:27
apwthey should so contain a version number15:28
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infinityppisati: Your awk magic for kvers comparisons is somewhat suspect.16:17
infinityppisati: I'm not so good with arithmetic, but I'm pretty sure that 2638 >> 311 >> 40, for instance.16:17
ppisatiinfinity: hold on16:18
ppisatiinfinity: i use just the first 2 number16:18
ppisatiinfinity: 26 < 311 < 4016:18
infinityWell, your first half is true. :P16:19
ppisatiinfinity: ah right :)16:19
ppisatiinfinity: well, when 4.0 is out we'll think about it :)16:19
infinityOr we can just do it right now.16:20
infinityI think I have some shell hackery in glibc to get this right.16:20
ppisatiinfinity: nice16:20
infinityOr you could just use dpkg --compare-versions, since having f-k without dpkg seems like an unlikely scenario.16:21
ppisatiinfinity: but then i need to know against which pkg i'm installing/overwriting16:22
infinityEh?16:22
infinityNo, dpkg --compare-versions just takes version arguments.16:23
infinityOr, there's this, from my glibc preinst:16:24
infinitylinux_compare_versions () {16:24
infinity    verA=$(($(echo "$1" | sed 's/^\([0-9]*\.[0-9]*\)\([^.0-9]\|$\)/\1.0\2/; s/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1 \* 10000 + \2 \* 100 + \3/')))16:24
infinity    verB=$(($(echo "$3" | sed 's/^\([0-9]*\.[0-9]*\)\([^.0-9]\|$\)/\1.0\2/; s/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1 \* 10000 + \2 \* 100 + \3/')))16:24
infinity    test $verA -$2 $verB16:24
infinity}16:24
infinityCAUSE THAT'S SUPER READABLE.16:24
ppisatiOH MY GOD!!!16:24
infinityI think I'll just use compare-versions.  I do that in initramfs-tools too.  It comes close enough to doing the right thing.16:25
infinityppisati: http://paste.ubuntu.com/6128952/16:31
ppisatiinfinity: way better, ack16:32
infinityI have no way to test that this actually works, but it looks sane enough to me.16:33
ppisatiinfinity: hold on16:33
infinity(I mean the overall patch, not my change)16:33
ppisatiinfinity: i tested the overll patch going from 2.6.35 to 3.11 (and back)16:35
infinityppisati: It will fail if $kernel already points to $tmpdir/kernel before your code triggers.16:37
infinityppisati: Which would happen in the machine_id case.16:37
infinityppisati: (Since you can't do "cat $foo > $foo")16:38
ppisatiinfinity: you mean the "append_dtb "$kernel" "$dtb" "$tmpdir/kernel""16:42
infinityppisati: Yeah, cause the previous block could have set $kernel to $tmpdir/kernel16:42
ppisatiinfinity: right16:42
infinity                                append_dtb "$kernel" "$dtb" "$tmpdir/kernel.dtb"16:42
infinity                                mv "$tmpdir/kernel.dtb" "$tmpdir/kernel"16:42
infinityThat seems like it would solve the issue.16:43
infinityThough maybe append_dtb itself should be more robust, so it doesn't let you do this.16:43
ppisatiinfinity: debian has the same problem16:44
ppisatihttp://anonscm.debian.org/gitweb/?p=d-i/flash-kernel.git;a=blob;f=functions;h=febf0d4af61dd59bb543798663f3f324d3c4fe68;hb=HEAD16:44
ppisatiline 50216:44
infinityIndeed.16:44
infinityWell, I'll fix it here for now. :P16:45
Notch-1hi, i'm having throuble using the full power of a bulldozer cpu: with sensors i see that when fam15h_power-pci-00c4 power1 reaches the crit value (125w) the cpu is slowed down and i get a serius performance drop. it's a kernel configuration thing?17:00
ppisatiinfinity: going out for dinner, see you later/tomorrow17:14
apwNotch-1, those thresholds normally come out of the cpu ... reaching crit thresholds normally are a very serious boundary and we would expect throttling19:11
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Notch-1apw: any way around that? 19:20
Notch-1apw: anyway it's odd: with another cpu with half the cores i have almost the same performance... and with this one the core/performance ratio it's stable until i use 5 core or more (out of 8). in other words i don't tink i'm getting the full power...19:25
apwNotch-1, or the pysical envelope isn't able to disipate the heat that device can produce efficiently enough21:19
apwie 6 cores can outstrip the cooling ...21:19
Notch-1apw: not a cooling issue, the heatpipe keeps the temperature below 60°...21:31
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