Okay so I think I mostly have a handle on the issue. The hardware problem is caused by the cpu running the sound card driver entering the c6 idle state. Anecdotally the card does not appear to be able to handle the latency involved in waking from that state. Currently, both intel_idle and acpi_idle cpuidle drivers handle this poorly wrt to this particular card/motherboard combo.
intel_idle: chronologically the first “break” occurred at commit 2671717265ae6e720a9ba5f13fbec3a718983b65 which switched the default cpuidle driver for intel machines from acpi_idle to intel_idle. According to https://lkml.org/lkml/2010/7/22/511 it seems the correct solution here is register idle constraints explicitly via PM_QOS in the linux device driver, my guess is in snd_ice1712. acpi_idle: the situation here is much less clear to me. The break here occurred at 718be4aaf3613cf7c2d097f925abc3d3553c0605 fixing bug 15886. That bug seems highly related since I have the same motherboard. I suspect the fault here lies in the bios, although since intel_idle was made the default before this commit, any bug introduced here would likely go unnoticed. I have various turbostat logs but will save those for the specific bugs I file. Also, the current “best workaround” is intel_idle.max_cstate=3. The reason nohz=off works is that it disables all cstates, but as long as we limit to c3 there is no apparent problem. ** Bug watch added: Linux Kernel Bug Tracker #15886 http://bugzilla.kernel.org/show_bug.cgi?id=15886 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/814426 Title: 1412:1712 Crackling Sound on PCI card Status in The Linux Kernel: New Status in “linux” package in Ubuntu: Incomplete Bug description: On my CyberpowerPC Gamer Xtreme 1030 desktop running up-to-date Natty Narwhal 64bit on fresh install, there is a variable crackling overlaying the sound on my card when any sound is playing. It is invariable to the output, as looping the same clip does not cause crackling to loop. The output of sudo aplay -l is: card 0: M1010LT [M Audio Delta 1010LT], device 0: ICE1712 multi [ICE1712 multi] Subdevices: 1/1 Subdevice #0: subdevice #0 Any idea's on what this is? Occurs with pulseaudio on or off (even with speaker-test), and only on my Delta 1010LT sound card. Jaunty livecd plays audio without crackles, while Natty livecd produces crackles. WORKAROUND: nohz=off --- AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23. AplayDevices: **** List of PLAYBACK Hardware Devices **** card 0: M1010LT [M Audio Delta 1010LT], device 0: ICE1712 multi [ICE1712 multi] Subdevices: 1/1 Subdevice #0: subdevice #0 Architecture: amd64 ArecordDevices: **** List of CAPTURE Hardware Devices **** card 0: M1010LT [M Audio Delta 1010LT], device 0: ICE1712 multi [ICE1712 multi] Subdevices: 1/1 Subdevice #0: subdevice #0 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: erik 2464 F.... pulseaudio /dev/snd/seq: erik 1737 F.... qjackctl CRDA: Error: [Errno 2] No such file or directory Card0.Amixer.info: Card hw:0 'M1010LT'/'M Audio Delta 1010LT at 0xdf00, irq 18' Mixer name : 'ICE1712 - multitrack' Components : '' Controls : 85 Simple ctrls : 57 DistroRelease: Ubuntu 11.04 HibernationDevice: RESUME=UUID=4362b0a7-9c03-48cc-a343-67976cd430cb InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1) IwConfig: lo no wireless extensions. eth0 no wireless extensions. MachineType: Gigabyte Technology Co., Ltd. P55M-UD2 NonfreeKernelModules: nvidia Package: linux (not installed) ProcEnviron: LANGUAGE=en_US:en LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-2.6.38-8-lowlatency root=UUID=903ba33e-b5c1-4749-ab76-e2f85a408b31 ro vga=769 quiet splash vt.handoff=7 ProcVersionSignature: Ubuntu 2.6.38-8.42~ppa2-lowlatency 2.6.38.2 RelatedPackageVersions: linux-restricted-modules-2.6.38-8-lowlatency N/A linux-backports-modules-2.6.38-8-lowlatency N/A linux-firmware 1.52 RfKill: Tags: natty Uname: Linux 2.6.38-8-lowlatency x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm admin audio cdrom dialout lpadmin plugdev sambashare dmi.bios.date: 06/23/2010 dmi.bios.vendor: Award Software International, Inc. dmi.bios.version: F11 dmi.board.name: P55M-UD2 dmi.board.vendor: Gigabyte Technology Co., Ltd. dmi.board.version: x.x dmi.chassis.type: 3 dmi.chassis.vendor: Gigabyte Technology Co., Ltd. dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF11:bd06/23/2010:svnGigabyteTechnologyCo.,Ltd.:pnP55M-UD2:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnP55M-UD2:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr: dmi.product.name: P55M-UD2 dmi.sys.vendor: Gigabyte Technology Co., Ltd. --- AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24. AplayDevices: **** List of PLAYBACK Hardware Devices **** card 0: M1010LT [M Audio Delta 1010LT], device 0: ICE1712 multi [ICE1712 multi] Subdevices: 1/1 Subdevice #0: subdevice #0 Architecture: amd64 AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/controlC0', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p', '/dev/snd/midiC0D0', '/dev/snd/by-path', '/dev/snd/by-id', '/dev/snd/controlC1', '/dev/snd/pcmC1D0c', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: CRDA: Error: [Errno 2] No such file or directory Card0.Amixer.info: Card hw:0 'M1010LT'/'M Audio Delta 1010LT at 0xdf00, irq 18' Mixer name : 'ICE1712 - multitrack' Components : '' Controls : 85 Simple ctrls : 57 Card1.Amixer.info: Card hw:1 'Camera'/'Vimicro Corp. Venus USB2.0 Camera at usb-0000:00:1a.7-4, high speed' Mixer name : 'USB Mixer' Components : 'USB0ac8:3420' Controls : 2 Simple ctrls : 1 Card1.Amixer.values: Simple mixer control 'Mic',0 Capabilities: cvolume cvolume-joined cswitch cswitch-joined penum Capture channels: Mono Limits: Capture 0 - 48 Mono: Capture 37 [77%] [on] CasperVersion: 1.272 DistroRelease: Ubuntu 11.10 IwConfig: lo no wireless extensions. eth0 no wireless extensions. LiveMediaBuild: Ubuntu 11.10 "Oneiric Ocelot" - Alpha amd64 (20110801) MachineType: Gigabyte Technology Co., Ltd. P55M-UD2 Package: linux (not installed) ProcEnviron: LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: file=/cdrom/preseed/hostname.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity ProcVersionSignature: Ubuntu 3.0.0-7.9-generic 3.0.0 RelatedPackageVersions: linux-restricted-modules-3.0.0-7-generic N/A linux-backports-modules-3.0.0-7-generic N/A linux-firmware 1.56 RfKill: Tags: oneiric running-unity Uname: Linux 3.0.0-7-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare dmi.bios.date: 06/23/2010 dmi.bios.vendor: Award Software International, Inc. dmi.bios.version: F11 dmi.board.name: P55M-UD2 dmi.board.vendor: Gigabyte Technology Co., Ltd. dmi.board.version: x.x dmi.chassis.type: 3 dmi.chassis.vendor: Gigabyte Technology Co., Ltd. dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF11:bd06/23/2010:svnGigabyteTechnologyCo.,Ltd.:pnP55M-UD2:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnP55M-UD2:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr: dmi.product.name: P55M-UD2 dmi.sys.vendor: Gigabyte Technology Co., Ltd. --- ApportVersion: 2.12.6-0ubuntu1 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC1: ubuntu 3505 F.... pulseaudio /dev/snd/controlC2: ubuntu 3505 F.... pulseaudio /dev/snd/controlC3: ubuntu 3505 F.... pulseaudio /dev/snd/controlC0: ubuntu 3505 F.... pulseaudio CasperVersion: 1.336ubuntu1 DistroRelease: Ubuntu 14.04 IwConfig: eth0 no wireless extensions. lo no wireless extensions. LiveMediaBuild: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20131111) MachineType: Gigabyte Technology Co., Ltd. P55M-UD2 MarkForUpload: True Package: linux (not installed) ProcFB: 0 nouveaufb ProcKernelCmdLine: initrd=/casper/initrd.lz file=/cdrom/preseed/username.seed boot=casper quiet splash -- BOOT_IMAGE=/casper/vmlinuz.efi ProcVersionSignature: Ubuntu 3.12.0-2.5-generic 3.12.0 RelatedPackageVersions: linux-restricted-modules-3.12.0-2-generic N/A linux-backports-modules-3.12.0-2-generic N/A linux-firmware 1.117 RfKill: Tags: trusty Uname: Linux 3.12.0-2-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo dmi.bios.date: 06/23/2010 dmi.bios.vendor: Award Software International, Inc. dmi.bios.version: F11 dmi.board.name: P55M-UD2 dmi.board.vendor: Gigabyte Technology Co., Ltd. dmi.board.version: x.x dmi.chassis.type: 3 dmi.chassis.vendor: Gigabyte Technology Co., Ltd. dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF11:bd06/23/2010:svnGigabyteTechnologyCo.,Ltd.:pnP55M-UD2:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnP55M-UD2:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr: dmi.product.name: P55M-UD2 dmi.sys.vendor: Gigabyte Technology Co., Ltd. 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