** Description changed: - $ cat /proc/version_signature + [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 + 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 + 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 + 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 + 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 + 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
** Summary changed: - mkfs.ext4 over /dev/bcache0 hangs + bcache: bch_allocator_thread(): hung task timeout -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1784665 Title: bcache: bch_allocator_thread(): hung task timeout To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1784665/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
