@ Ryan we do not test Xenial or Disco

On Thu, Aug 22, 2019 at 7:41 PM Ryan Harper <email address hidden>
wrote:

> Finally, I did verify xenial proposed with our original test.  I had
> over 100 installs with no issue.
>
> @Jason
>
> Have you had any runs on Xenial or Disco?  (or do you not test those)?
>
> --
> You received this bug notification because you are a member of Canonical
> Field Critical, which is subscribed to a duplicate bug report (1796292).
> https://bugs.launchpad.net/bugs/1784665
>
> Title:
>   bcache: bch_allocator_thread(): hung task timeout
>
> Status in linux package in Ubuntu:
>   Fix Committed
> Status in linux source package in Xenial:
>   Fix Committed
> Status in linux source package in Bionic:
>   New
> Status in linux source package in Disco:
>   Fix Committed
> Status in linux source package in Eoan:
>   Fix Committed
>
> Bug description:
>   [Impact]
>
>   bcache_allocator() can call the following:
>
>    bch_allocator_thread()
>     -> bch_prio_write()
>        -> bch_bucket_alloc()
>           -> wait on &ca->set->bucket_wait
>
>   But the wake up event on bucket_wait is supposed to come from
> bch_allocator_thread() itself causing a deadlock.
>
>   [Test Case]
>
>   This is a simple script that can easily trigger the deadlock condition:
>   https://launchpadlibrarian.net/381282009/bcache-basic-repro.sh
>
>   A better test case has been also provided in bug 1796292 (duplicate of
> this bug):
>
> https://bugs.launchpad.net/curtin/+bug/1796292/+attachment/5280353/+files/curtin-nvme.sh
>
>   [Fix]
>
>   Fix by making the call to bch_prio_write() non-blocking, so that
>   bch_allocator_thread() never waits on itself. Moreover, make sure to
>   wake up the garbage collector thread when bch_prio_write() is failing
>   to allocate buckets to increase the chance of freeing up more buckets.
>
>   In addition to that it would be safe to also import other upstream
>   bcache fixes (all clean cherry picks):
>
>   7e865eba00a3df2dc8c4746173a8ca1c1c7f042e bcache: fix potential deadlock
> in cached_def_free()
>   80265d8dfd77792e133793cef44a21323aac2908 bcache: acquire
> bch_register_lock later in cached_dev_free()
>   ce4c3e19e5201424357a0c82176633b32a98d2ec bcache: Replace
> bch_read_string_list() by __sysfs_match_string()
>   ecb37ce9baac653cc09e2b631393dde3df82979f bcache: Move couple of
> functions to sysfs.c
>   04cbc21137bfa4d7b8771a5b14f3d6c9b2aee671 bcache: Move couple of string
> arrays to sysfs.c
>   5f2b18ec8e1643410a2369f06888951cdedea0bf bcache: Fix a compiler warning
> in bcache_device_init()
>   20d3a518713e394efa5a899c84574b4b79ec5098 bcache: Reduce the number of
> sparse complaints about lock imbalances
>   42361469ae84c851e40cb1f94c8c9a14cdd94039 bcache: Suppress more warnings
> about set-but-not-used variables
>   f0d3814090ac77de94c42b7124c37ece23629197 bcache: Remove an unused
> variable
>   47344e330eabc1515cbe6061eb337100a3ab6d37 bcache: Fix kernel-doc warnings
>   9dfbdec7b7fea1ff1b7b5d5d12980dbc7dca46c7 bcache: Annotate switch
> fall-through
>   4a4e443835a43a79113cc237c472c0d268eb1e1c bcache: Add __printf annotation
> to __bch_check_keys()
>   fd01991d5c20098c5c1ffc4dca6c821cc60a2f74 bcache: Fix indentation
>   ca71df31661a0518ed58a1a59cf1993962153ebb bcache: fix using of loop
> variable in memory shrink
>   f3641c3abd1da978ee969b0203b71b86ec1bfa93 bcache: fix error return value
> in memory shrink
>   688892b3bc05e25da94866e32210e5f503f16f69 bcache: fix incorrect sysfs
> output value of strip size
>   09a44ca2114737e0932257619c16a2b50c7807f1 bcache: use pr_info() to inform
> duplicated CACHE_SET_IO_DISABLE set
>   c4dc2497d50d9c6fb16aa0d07b6a14f3b2adb1e0 bcache: fix high CPU occupancy
> during journal
>   a728eacbbdd229d1d903e46261c57d5206f87a4a bcache: add journal statistic
>   616486ab52ab7f9739b066d958bdd20e65aefd74 bcache: fix writeback target
> calc on large devices
>   1f0ffa67349c56ea54c03ccfd1e073c990e7411e bcache: only set
> BCACHE_DEV_WB_RUNNING when cached device attached
>   eb8cbb6df38f6e5124a3d5f1f8a3dbf519537c60 bcache: improve bcache_reboot()
>   9951379b0ca88c95876ad9778b9099e19a95d566 bcache: never writeback a
> discard operation
>
>   [Regression Potential]
>
>   The upstream fixes are all clean cherry picks from stable (most of
>   them are small cleanups), so regression potential is minimal.
>
>   The only special patch is "UBUNTU: SAUCE: bcache: fix deadlock in
>   bcache_allocator()" that is addressing the main deadlock bug (that
>   seems to be a mainline bug - not fixed yet). We should spend more time
>   trying to reproduce this deadlock with a mainline kernel and post the
>   patch to the LKML for review / feedback.
>
>   However, considering that this patch seems to fix/prevent the specific
>   deadlock problem reported in this bug (tested on the affected
>   platform) it can be considered safe to apply it.
>
>   [Original Bug Report]
>
>   $ cat /proc/version_signature
>   Ubuntu 4.15.0-29.31-generic 4.15.18
>
>   $ lsb_release -rd
>   Description:  Ubuntu Cosmic Cuttlefish (development branch)
>   Release:      18.10
>
>   $ apt-cache policy linux-image-`uname -r`
>   linux-image-4.15.0-29-generic:
>     Installed: 4.15.0-29.31
>     Candidate: 4.15.0-29.31
>     Version table:
>    *** 4.15.0-29.31 500
>           500 http://archive.ubuntu.com/ubuntu cosmic/main amd64 Packages
>           100 /var/lib/dpkg/status
>
>   3) mkfs.ext4 /dev/bcache0 returns successful creating an ext4
>   filesystem on top of a bcache device
>
>   4) mkfs.ext4 doesn't return and kernel prints hung process info
>
>   [   58.018099] cloud-init[920]: Running command ['mkfs.ext4', '-F',
> '-L', 'root-fs', '-U', 'f01aec97-9457-11e8-b8d6-525400123401',
> '/dev/bcache0'] with allowed return codes [0] (capture=True)
>   [  242.652018] INFO: task kworker/u4:0:5 blocked for more than 120
> seconds.
>   [  242.653767]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  242.655391] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  242.657397] INFO: task kworker/0:2:410 blocked for more than 120
> seconds.
>   [  242.659126]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  242.660980] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  242.663000] INFO: task bcache_allocato:2326 blocked for more than 120
> seconds.
>   [  242.664807]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  242.666516] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  242.668503] INFO: task bcache_writebac:2345 blocked for more than 120
> seconds.
>   [  242.670301]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  242.671936] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  242.673909] INFO: task mkfs.ext4:2803 blocked for more than 120
> seconds.
>   [  242.675414]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  242.677038] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  363.483998] INFO: task kworker/u4:0:5 blocked for more than 120
> seconds.
>   [  363.488441]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  363.489598] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  363.491043] INFO: task kworker/0:2:410 blocked for more than 120
> seconds.
>   [  363.492252]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  363.494085] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  363.495659] INFO: task bcache_allocato:2326 blocked for more than 120
> seconds.
>   [  363.496957]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  363.498454] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  363.499866] INFO: task bcache_writebac:2345 blocked for more than 120
> seconds.
>   [  363.501156]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  363.502597] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>   [  363.504048] INFO: task mkfs.ext4:2803 blocked for more than 120
> seconds.
>   [  363.505505]       Tainted: P           O     4.15.0-29-generic
> #31-Ubuntu
>   [  363.506677] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
>
>   System has two virtio block devices.  bcache was created like so:
>
>   make-bcache -C /dev/vdb
>   make-bcache -B /dev/vda2
>
>   resulting in /dev/bcache0
>
>   ProblemType: Bug
>   DistroRelease: Ubuntu 18.10
>   Package: linux-image-4.15.0-29-generic 4.15.0-29.31
>   ProcVersionSignature: User Name 4.15.0-29.31-generic 4.15.18
>   Uname: Linux 4.15.0-29-generic x86_64
>   AlsaDevices:
>    total 0
>    crw-rw---- 1 root audio 116,  1 Jul 31 15:52 seq
>    crw-rw---- 1 root audio 116, 33 Jul 31 15:52 timer
>   AplayDevices: Error: [Errno 2] No such file or directory: 'aplay':
> 'aplay'
>   ApportVersion: 2.20.10-0ubuntu7
>   Architecture: amd64
>   ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord':
> 'arecord'
>   AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq',
> '/dev/snd/timer'] failed with exit code 1:
>   CRDA: N/A
>   Date: Tue Jul 31 15:53:56 2018
>   IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig':
> 'iwconfig'
>   Lsusb: Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
>   MachineType: QEMU Standard PC (i440FX + PIIX, 1996)
>   PciMultimedia:
>
>   ProcEnviron:
>    TERM=xterm
>    PATH=(custom, no user)
>    XDG_RUNTIME_DIR=<set>
>    LANG=C.UTF-8
>    SHELL=/bin/bash
>   ProcFB:
>
>   ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-29-generic
> root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0
>   RelatedPackageVersions:
>    linux-restricted-modules-4.15.0-29-generic N/A
>    linux-backports-modules-4.15.0-29-generic  N/A
>    linux-firmware                             N/A
>   RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
>   SourcePackage: linux
>   UpgradeStatus: No upgrade log present (probably fresh install)
>   dmi.bios.date: 04/01/2014
>   dmi.bios.vendor: SeaBIOS
>   dmi.bios.version: 1.11.1-1
>   dmi.chassis.type: 1
>   dmi.chassis.vendor: QEMU
>   dmi.chassis.version: pc-i440fx-bionic
>   dmi.modalias:
> dmi:bvnSeaBIOS:bvr1.11.1-1:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-bionic:cvnQEMU:ct1:cvrpc-i440fx-bionic:
>   dmi.product.name: Standard PC (i440FX + PIIX, 1996)
>   dmi.product.version: pc-i440fx-bionic
>   dmi.sys.vendor: QEMU
>
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