I'm thinking of a way to debug this too. The symptom may hint at a use-after-free. Could you enable KASAN in your tests? (On the flip side, I know this might change timings, thereby making the fault disappear). Thanks, Paolo > Il giorno 5 mar 2021, alle ore 10:27, Ming Lei <tom.leiming@xxxxxxxxx> ha scritto: > > Hello Hillf, > > Thanks for the debug patch. > > On Fri, Mar 5, 2021 at 5:00 PM Hillf Danton <hdanton@xxxxxxxx> wrote: >> >> On Thu, 4 Mar 2021 16:42:30 +0800 Ming Lei wrote: >>> On Sat, Oct 10, 2020 at 1:40 PM Mikhail Gavrilov >>> <mikhail.v.gavrilov@xxxxxxxxx> wrote: >>>> >>>> Paolo, Jens I am sorry for the noise. >>>> But today I hit the kernel panic and git blame said that you have >>>> created the file in which happened panic (this I saw from trace) >>>> >>>> $ /usr/src/kernels/`uname -r`/scripts/faddr2line >>>> /lib/debug/lib/modules/`uname -r`/vmlinux >>>> __bfq_deactivate_entity+0x15a >>>> __bfq_deactivate_entity+0x15a/0x240: >>>> bfq_gt at block/bfq-wf2q.c:20 >>>> (inlined by) bfq_insert at block/bfq-wf2q.c:381 >>>> (inlined by) bfq_idle_insert at block/bfq-wf2q.c:621 >>>> (inlined by) __bfq_deactivate_entity at block/bfq-wf2q.c:1203 >>>> >>>> https://github.com/torvalds/linux/blame/master/block/bfq-wf2q.c#L1203 >>>> >>>> $ head /sys/block/*/queue/scheduler >>>> ==> /sys/block/nvme0n1/queue/scheduler <== >>>> [none] mq-deadline kyber bfq >>>> >>>> ==> /sys/block/sda/queue/scheduler <== >>>> mq-deadline kyber [bfq] none >>>> >>>> ==> /sys/block/zram0/queue/scheduler <== >>>> none >>>> >>>> Trace: >>>> general protection fault, probably for non-canonical address >>>> 0x46b1b0f0d8856e4a: 0000 [#1] SMP NOPTI >>>> CPU: 27 PID: 1018 Comm: kworker/27:1H Tainted: G W >>>> --------- --- 5.9.0-0.rc8.28.fc34.x86_64 #1 >>>> Hardware name: System manufacturer System Product Name/ROG STRIX >>>> X570-I GAMING, BIOS 2606 08/13/2020 >>>> Workqueue: kblockd blk_mq_run_work_fn >>>> RIP: 0010:__bfq_deactivate_entity+0x15a/0x240 >>>> Code: 48 2b 41 28 48 85 c0 7e 05 49 89 5c 24 18 49 8b 44 24 08 4d 8d >>>> 74 24 08 48 85 c0 0f 84 d6 00 00 00 48 8b 7b 28 eb 03 48 89 c8 <48> 8b >>>> 48 28 48 8d 70 10 48 8d 50 08 48 29 f9 48 85 c9 48 0f 4f d6 >>>> RSP: 0018:ffffadf6c0c6fc00 EFLAGS: 00010002 >>>> RAX: 46b1b0f0d8856e4a RBX: ffff8dc2773b5c88 RCX: 46b1b0f0d8856e4a >>>> RDX: ffff8dc7d02ed0a0 RSI: ffff8dc7d02ed0a8 RDI: 0000584e64e96beb >>>> RBP: ffff8dc2773b5c00 R08: ffff8dc9054cb938 R09: 0000000000000000 >>>> R10: 0000000000000018 R11: 0000000000000018 R12: ffff8dc904927150 >>>> R13: 0000000000000001 R14: ffff8dc904927158 R15: ffff8dc2773b5c88 >>>> FS: 0000000000000000(0000) GS:ffff8dc90e0c0000(0000) knlGS:0000000000000000 >>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>> CR2: 0000003e8ebe4000 CR3: 00000007c2546000 CR4: 0000000000350ee0 >>>> Call Trace: >>>> bfq_deactivate_entity+0x4f/0xc0 >>> >>> Hello, >>> >>> The same stack trace was observed in RH internal test too, and kernel >>> is 5.11.0-0.rc6, >>> but there isn't reproducer yet. >>> >>> >>> -- >>> Ming Lei >> >> Add some debug info. >> >> --- x/block/bfq-wf2q.c >> +++ y/block/bfq-wf2q.c >> @@ -647,8 +647,10 @@ static void bfq_forget_entity(struct bfq >> >> entity->on_st_or_in_serv = false; >> st->wsum -= entity->weight; >> - if (bfqq && !is_in_service) >> + if (bfqq && !is_in_service) { >> + WARN_ON(entity->tree != NULL); >> bfq_put_queue(bfqq); >> + } >> } >> >> /** >> @@ -1631,6 +1633,7 @@ bool __bfq_bfqd_reset_in_service(struct >> * bfqq gets freed here. >> */ >> int ref = in_serv_bfqq->ref; >> + WARN_ON(in_serv_entity->tree != NULL); >> bfq_put_queue(in_serv_bfqq); >> if (ref == 1) >> return true; > > This kernel oops isn't easy to be reproduced, and we have got another crash > report[1] too, still on __bfq_deactivate_entity(), and not easy to > trigger. Can your > debug patch cover the report[1]? If not, feel free to add more debug messages, > then I will try to reproduce the two. > > [1] another kernel oops log on __bfq_deactivate_entity > > [ 899.790606] systemd-sysv-generator[25205]: SysV service > '/etc/rc.d/init.d/anamon' lacks a native systemd unit file. > Automatically generating a unit file for compatibility. Please update > package to include a native systemd unit file, in order to make it > more safe and robust. > [ 901.937047] BUG: kernel NULL pointer dereference, address: 0000000000000000 > [ 901.944005] #PF: supervisor read access in kernel mode > [ 901.949143] #PF: error_code(0x0000) - not-present page > [ 901.954285] PGD 0 P4D 0 > [ 901.956824] Oops: 0000 [#1] SMP NOPTI > [ 901.960490] CPU: 13 PID: 22966 Comm: kworker/13:0 Tainted: G > I X --------- --- 5.11.0-1.el9.x86_64 #1 > [ 901.970829] Hardware name: Dell Inc. PowerEdge R740xd/0WXD1Y, BIOS > 2.5.4 01/13/2020 > [ 901.978480] Workqueue: cgwb_release cgwb_release_workfn > [ 901.983705] RIP: 0010:__bfq_deactivate_entity+0x5b/0x240 > [ 901.989016] Code: b8 30 00 00 00 75 18 48 81 ff 88 00 00 00 74 0f > 0f b7 47 8a 83 e8 01 48 8d 04 40 48 c1 e0 04 4c 8b 73 68 48 63 73 40 > 48 89 df <4d> 8b 3e 4d 8d 64 06 10 e8 48 f0 ff ff 49 39 df 0f 84 87 01 > 00 00 > [ 902.007763] RSP: 0018:ffffb77107f0bd98 EFLAGS: 00010002 > [ 902.012986] RAX: 0000002fffffffd0 RBX: ffff9853ca9c6098 RCX: 0000000000000046 > [ 902.020119] RDX: 0000000000000001 RSI: 00000000474b1168 RDI: ffff9853ca9c6098 > [ 902.027253] RBP: 0000000000000000 R08: 0000000000000000 R09: ffff985470c2fed0 > [ 902.034383] R10: 0000000000000001 R11: ffff9853c9287d98 R12: ffff9853ca8b8000 > [ 902.041515] R13: 00000000000000ff R14: 0000000000000000 R15: ffff985b44308098 > [ 902.048647] FS: 0000000000000000(0000) GS:ffff98631f980000(0000) > knlGS:0000000000000000 > [ 902.056732] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 902.062479] CR2: 0000000000000000 CR3: 00000001c0ac2002 CR4: 00000000007706e0 > [ 902.069611] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 902.076744] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 902.083876] PKRU: 55555554 > [ 902.086589] Call Trace: > [ 902.089042] bfq_pd_offline+0x89/0xd0 > [ 902.092708] blkg_destroy+0x52/0xf0 > [ 902.096200] blkcg_destroy_blkgs+0x46/0xc0 > [ 902.100300] cgwb_release_workfn+0xbe/0x150 > [ 902.104485] process_one_work+0x1e6/0x380 > [ 902.108497] worker_thread+0x53/0x3d0 > [ 902.112161] ? process_one_work+0x380/0x380 > [ 902.116346] kthread+0x11b/0x140 > [ 902.119581] ? kthread_associate_blkcg+0xa0/0xa0 > [ 902.124199] ret_from_fork+0x1f/0x30 > [ 902.127780] Modules linked in: sunrpc scsi_debug iscsi_tcp > libiscsi_tcp libiscsi scsi_transport_iscsi nft_reject_inet > nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat > nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink > rfkill intel_rapl_msr intel_rapl_common isst_if_common skx_edac nfit > libnvdimm x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm > ipmi_ssif irqbypass mgag200 rapl i2c_algo_bit iTCO_wdt drm_kms_helper > intel_cstate iTCO_vendor_support syscopyarea sysfillrect sysimgblt > acpi_ipmi mei_me fb_sys_fops intel_uncore pcspkr dell_smbios dcdbas > dell_wmi_descriptor wmi_bmof mei cec i2c_i801 ipmi_si acpi_power_meter > lpc_ich i2c_smbus ipmi_devintf ipmi_msghandler drm fuse xfs libcrc32c > sd_mod t10_pi crct10dif_pclmul crc32_pclmul crc32c_intel ahci libahci > megaraid_sas tg3 ghash_clmulni_intel libata wmi dm_mirror > dm_region_hash dm_log dm_mod [last unloaded: ip_tables] > [ 902.208546] CR2: 0000000000000000 > [ 902.211881] ---[ end trace 827b8521dc634ca4 ]--- > > > -- > Ming Lei
