On Thu, 2021-12-30 at 13:24 -0800, Jens Axboe wrote: > On 12/30/21 11:35 AM, trondmy@xxxxxxxxxx wrote: > > From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> > > > > We're observing the following stack trace using various kernels > > when > > running in the Azure cloud. > > > > watchdog: BUG: soft lockup - CPU#12 stuck for 23s! > > [kworker/12:1:3106] > > Modules linked in: raid0 ipt_MASQUERADE nf_conntrack_netlink > > xt_addrtype nft_chain_nat nf_nat br_netfilter bridge stp llc ext4 > > mbcache jbd2 overlay xt_conntrack nf_conntrack nf_defrag_ipv6 > > nf_defrag_ipv4 nft_counter rpcrdma rdma_ucm xt_owner ib_srpt > > nft_compat intel_rapl_msr ib_isert intel_rapl_common nf_tables > > iscsi_target_mod isst_if_mbox_msr isst_if_common nfnetlink > > target_core_mod nfit ib_iser libnvdimm libiscsi > > scsi_transport_iscsi ib_umad kvm_intel ib_ipoib rdma_cm iw_cm vfat > > ib_cm fat kvm irqbypass crct10dif_pclmul crc32_pclmul mlx5_ib > > ghash_clmulni_intel rapl ib_uverbs ib_core i2c_piix4 pcspkr > > hyperv_fb hv_balloon hv_utils joydev nfsd auth_rpcgss nfs_acl lockd > > grace sunrpc ip_tables xfs libcrc32c mlx5_core mlxfw tls pci_hyperv > > pci_hyperv_intf sd_mod t10_pi sg ata_generic hv_storvsc hv_netvsc > > scsi_transport_fc hyperv_keyboard hid_hyperv ata_piix libata > > crc32c_intel hv_vmbus serio_raw fuse > > CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0- > > 305.10.2.el8_4.x86_64 #1 > > Hardware name: Microsoft Corporation Virtual Machine/Virtual > > Machine, BIOS 090008 12/07/2018 > > Workqueue: xfs-conv/md127 xfs_end_io [xfs] > > RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20 > > Code: 7c ff 48 29 e8 4c 39 e0 76 cf 80 0b 08 eb 8c 90 90 90 90 90 > > 90 90 90 90 90 0f 1f 44 00 00 e8 e6 db 7e ff 66 90 48 89 f7 57 9d > > <0f> 1f 44 00 00 c3 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 8b 07 > > RSP: 0018:ffffac51d26dfd18 EFLAGS: 00000202 ORIG_RAX: > > ffffffffffffff12 > > RAX: 0000000000000001 RBX: ffffffff980085a0 RCX: dead000000000200 > > RDX: ffffac51d3893c40 RSI: 0000000000000202 RDI: 0000000000000202 > > RBP: 0000000000000202 R08: ffffac51d3893c40 R09: 0000000000000000 > > R10: 00000000000000b9 R11: 00000000000004b3 R12: 0000000000000a20 > > R13: ffffd228f3e5a200 R14: ffff963cf7f58d10 R15: ffffd228f3e5a200 > > FS: 0000000000000000(0000) GS:ffff9625bfb00000(0000) > > knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00007f5035487500 CR3: 0000000432810004 CR4: 00000000003706e0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > wake_up_page_bit+0x8a/0x110 > > iomap_finish_ioend+0xd7/0x1c0 > > iomap_finish_ioends+0x7f/0xb0 > > xfs_end_ioend+0x6b/0x100 [xfs] > > ? xfs_setfilesize_ioend+0x60/0x60 [xfs] > > xfs_end_io+0xb9/0xe0 [xfs] > > process_one_work+0x1a7/0x360 > > worker_thread+0x1fa/0x390 > > ? create_worker+0x1a0/0x1a0 > > kthread+0x116/0x130 > > ? kthread_flush_work_fn+0x10/0x10 > > ret_from_fork+0x35/0x40 > > > > Jens suggested adding a latency-reducing cond_resched() to the loop > > in > > iomap_finish_ioends(). > > The patch doesn't add it there though, I was suggesting: > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 71a36ae120ee..4ad2436a936a 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -1078,6 +1078,7 @@ iomap_finish_ioends(struct iomap_ioend *ioend, > int error) > ioend = list_first_entry(&tmp, struct iomap_ioend, > io_list); > list_del_init(&ioend->io_list); > iomap_finish_ioend(ioend, error); > + cond_resched(); > } > } > EXPORT_SYMBOL_GPL(iomap_finish_ioends); > > as I don't think you need it once-per-vec. But not sure if you tested > that variant or not... > Yes, we did test that variant, but were still seeing the soft lockups on Azure, hence why I moved it into the inner loop. -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
