** Tags added: bios-outdated-2.6.1 needs-upstream-testing regression- release
-- 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/1064521 Title: Kernel I/O scheduling writes starving reads, local DoS Status in “linux” package in Ubuntu: Triaged Status in “linux” source package in Precise: Triaged Status in “linux” source package in Quantal: Triaged Bug description: On the Precise default kernel, it is possible by executing zcat on a large file for an unprivileged user to disrupt I/O sufficiently that it causes serious disruption. Serious disruption means (e.g.) a single MySQL update hangs for over 120 seconds on the default scheduler (cfq), and between 1 and 11 seconds on the deadline scheduler. This is reproducible on 2 sets of hardware using: root@extility-qa-test:~# uname -a Linux extility-qa-test 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux linux-image-3.2.0-29-generic 3.2.0-29.46 root@extility-qa-test:~# cat /proc/sys/vm/dirty_ratio 20 root@extility-qa-test:~# cat /proc/sys/vm/dirty_background_ratio 10 No such problems occur on Lucid OS running the Oneiric Backports kernel. root@management-dev2:~# uname -a Linux management-dev2 3.0.0-15-server #26~lucid1-Ubuntu SMP Wed Jan 25 15:55:45 UTC 2012 x86_64 GNU/Linux linux-image-3.0.0-15-server 3.0.0-15.26~lucid1 In order to replicate, download (e.g.) this gzipped Lucid image (note this is not the OS we are running, this is just an example of the a file that causes the problem): http://repo.flexiant.com/images/public/kvm/ubuntu10.04.img.gz and as un unprivileged user, on a default, untuned Precise install, do zcat ubuntu10.04.img.gz > test Now in another window execute any trivial mysql update on any table. Note that this can take a hugely long time. "show full processlist" in mysql console will show the time taken executing the command. In kernel logs (with cfq) we see e.g.: Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268048] INFO: task mysqld:1358 blocked for more than 120 seconds. Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268144] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268267] mysqld D ffffffff81806200 0 1358 1 0x00000000 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268272] ffff8801921fde48 0000000000000082 ffff8801921fde00 0000000300000001 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268278] ffff8801921fdfd8 ffff8801921fdfd8 ffff8801921fdfd8 0000000000013780 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268283] ffff880195169700 ffff880191f79700 ffff8801921fde58 ffff8801912b2800 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268288] Call Trace: Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268298] [<ffffffff816579cf>] schedule+0x3f/0x60 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268303] [<ffffffff812650d5>] jbd2_log_wait_commit+0xb5/0x130 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268308] [<ffffffff8108aa50>] ? add_wait_queue+0x60/0x60 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268313] [<ffffffff81211248>] ext4_sync_file+0x208/0x2d0 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268317] [<ffffffff81177ba0>] ? vfs_write+0x110/0x180 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268321] [<ffffffff811a63a6>] do_fsync+0x56/0x80 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268325] [<ffffffff811a66d0>] sys_fsync+0x10/0x20 Oct 8 14:57:02 extility-qa-test kernel: [ 3840.268329] [<ffffffff81661ec2>] system_call_fastpath+0x16/0x1b Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268176] INFO: task mysqld:1358 blocked for more than 120 seconds. Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268282] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268393] mysqld D ffffffff81806200 0 1358 1 0x00000000 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268399] ffff8801921fde48 0000000000000082 ffff8801921fde00 0000000300000001 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268405] ffff8801921fdfd8 ffff8801921fdfd8 ffff8801921fdfd8 0000000000013780 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268410] ffff880195169700 ffff880191f79700 ffff8801921fde58 ffff8801912b2800 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268415] Call Trace: Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268426] [<ffffffff816579cf>] schedule+0x3f/0x60 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268431] [<ffffffff812650d5>] jbd2_log_wait_commit+0xb5/0x130 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268436] [<ffffffff8108aa50>] ? add_wait_queue+0x60/0x60 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268441] [<ffffffff81211248>] ext4_sync_file+0x208/0x2d0 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268445] [<ffffffff81177ba0>] ? vfs_write+0x110/0x180 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268450] [<ffffffff811a63a6>] do_fsync+0x56/0x80 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268454] [<ffffffff811a66d0>] sys_fsync+0x10/0x20 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268458] [<ffffffff81661ec2>] system_call_fastpath+0x16/0x1b Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268473] INFO: task master:1525 blocked for more than 120 seconds. Oct 8 14:59:02 extility-qa-test kernel: [ 3960.268563] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. This isn't just a problem with MySQL. Here it is killing Postgres: Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269090] INFO: task postgres:2188 blocked for more than 120 seconds. Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269188] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269298] postgres D ffffffff81806200 0 2188 2186 0x00000000 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269302] ffff8801919cbe48 0000000000000082 ffff8801919cbe00 0000000300000001 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269307] ffff8801919cbfd8 ffff8801919cbfd8 ffff8801919cbfd8 0000000000013780 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269312] ffff880195169700 ffff8801916fae00 ffff8801919cbe58 ffff8801912b2800 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269317] Call Trace: Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269321] [<ffffffff816579cf>] schedule+0x3f/0x60 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269325] [<ffffffff812650d5>] jbd2_log_wait_commit+0xb5/0x130 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269328] [<ffffffff8108aa50>] ? add_wait_queue+0x60/0x60 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269332] [<ffffffff81211248>] ext4_sync_file+0x208/0x2d0 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269335] [<ffffffff81177ba0>] ? vfs_write+0x110/0x180 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269339] [<ffffffff811a63a6>] do_fsync+0x56/0x80 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269342] [<ffffffff811a66d0>] sys_fsync+0x10/0x20 Oct 8 14:59:02 extility-qa-test kernel: [ 3960.269346] [<ffffffff81661ec2>] system_call_fastpath+0x16/0x1b Standard information follows: root@extility-qa-test:~# lsb_release -rd Description: Ubuntu 12.04.1 LTS Release: 12.04 root@extility-qa-test:~# apt-cache policy linux-image-3.2.0-29-generic linux-image-3.2.0-29-generic: Installed: 3.2.0-29.46 Candidate: 3.2.0-29.46 Version table: *** 3.2.0-29.46 0 500 http://gb.archive.ubuntu.com/ubuntu/ precise-updates/main amd64 Packages 500 http://security.ubuntu.com/ubuntu/ precise-security/main amd64 Packages 100 /var/lib/dpkg/status Expected behaviour: same as Lucid, perhaps MySQL slows down a bit, but cannot be DoS'd What actually happened: local DoS of MySQL. --- AlsaDevices: total 0 crw-rw---T 1 root audio 116, 1 Oct 9 10:02 seq crw-rw---T 1 root audio 116, 33 Oct 9 10:02 timer AplayDevices: Error: [Errno 2] No such file or directory ApportVersion: 2.0.1-0ubuntu13 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: CRDA: Error: [Errno 2] No such file or directory DistroRelease: Ubuntu 12.04 HibernationDevice: RESUME=UUID=5cd80c3d-3646-42ed-bf16-528a0151228d InstallationMedia: Ubuntu-Server 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120817.3) IwConfig: Error: [Errno 2] No such file or directory MachineType: Dell Inc. PowerEdge R210 II Package: linux (not installed) PciMultimedia: ProcEnviron: LANGUAGE=en_GB:en TERM=xterm-color LANG=en_GB.UTF-8 SHELL=/bin/bash ProcFB: 0 VESA VGA ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-29-generic root=UUID=9daecda1-1f0f-41a0-91b8-5981fdea5c9e ro quiet ProcVersionSignature: Ubuntu 3.2.0-29.46-generic 3.2.24 RelatedPackageVersions: linux-restricted-modules-3.2.0-29-generic N/A linux-backports-modules-3.2.0-29-generic N/A linux-firmware 1.79 RfKill: Error: [Errno 2] No such file or directory Tags: precise Uname: Linux 3.2.0-29-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: dmi.bios.date: 03/13/2012 dmi.bios.vendor: Dell Inc. dmi.bios.version: 2.0.5 dmi.board.name: 03X6X0 dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 23 dmi.chassis.vendor: Dell Inc. dmi.modalias: dmi:bvnDellInc.:bvr2.0.5:bd03/13/2012:svnDellInc.:pnPowerEdgeR210II:pvr:rvnDellInc.:rn03X6X0:rvrA00:cvnDellInc.:ct23:cvr: dmi.product.name: PowerEdge R210 II dmi.sys.vendor: Dell Inc. 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