Re: [PATCH v6 1/4] rcu: Make call_rcu() lazy to save power

Joel Fernandes
2022-09-27T22:05:26Z

> On Sep 27, 2022, at 5:31 PM, Uladzislau Rezki <urezki@gmail.com> wrote:
>
> ﻿On Tue, Sep 27, 2022 at 05:13:34PM +0200, Uladzislau Rezki wrote:
>>> On Tue, Sep 27, 2022 at 04:59:44PM +0200, Uladzislau Rezki wrote:
>>> On Tue, Sep 27, 2022 at 02:30:03PM +0000, Joel Fernandes wrote:
>>>> On Tue, Sep 27, 2022 at 04:08:18PM +0200, Uladzislau Rezki wrote:
>>>>> On Mon, Sep 26, 2022 at 08:54:27PM +0000, Joel Fernandes wrote:
>>>>>> Hi Vlad,
>>>>>>
>>>>>> On Mon, Sep 26, 2022 at 09:39:23PM +0200, Uladzislau Rezki wrote:
>>>>>> [...]
>>>>>>>>> On my KVM machine the boot time is affected:
>>>>>>>>>
>>>>>>>>> <snip>
>>>>>>>>> [ 2.273406] e1000 0000:00:03.0 eth0: Intel(R) PRO/1000 Network Connection
>>>>>>>>> [ 11.945283] e1000 0000:00:03.0 ens3: renamed from eth0
>>>>>>>>> [ 22.165198] sr 1:0:0:0: [sr0] scsi3-mmc drive: 4x/4x cd/rw xa/form2 tray
>>>>>>>>> [ 22.165206] cdrom: Uniform CD-ROM driver Revision: 3.20
>>>>>>>>> [ 32.406981] sr 1:0:0:0: Attached scsi CD-ROM sr0
>>>>>>>>> [ 104.115418] process '/usr/bin/fstype' started with executable stack
>>>>>>>>> [ 104.170142] EXT4-fs (sda1): mounted filesystem with ordered data mode. Quota mode: none.
>>>>>>>>> [ 104.340125] systemd[1]: systemd 241 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD -IDN2 +IDN -PCRE2 default-hierarchy=hybrid)
>>>>>>>>> [ 104.340193] systemd[1]: Detected virtualization kvm.
>>>>>>>>> [ 104.340196] systemd[1]: Detected architecture x86-64.
>>>>>>>>> [ 104.359032] systemd[1]: Set hostname to <pc638>.
>>>>>>>>> [ 105.740109] random: crng init done
>>>>>>>>> [ 105.741267] systemd[1]: Reached target Remote File Systems.
>>>>>>>>> <snip>
>>>>>>>>>
>>>>>>>>> 2 - 11 and second delay is between 32 - 104. So there are still users which must
>>>>>>>>> be waiting for "RCU" in a sync way.
>>>>>>>>
>>>>>>>> I was wondering if you can compare boot logs and see which timestamp does the
>>>>>>>> slow down start from. That way, we can narrow down the callback. Also another
>>>>>>>> idea is, add "trace_event=rcu:rcu_callback,rcu:rcu_invoke_callback
>>>>>>>> ftrace_dump_on_oops" to the boot params, and then manually call
>>>>>>>> "tracing_off(); panic();" from the code at the first printk that seems off in
>>>>>>>> your comparison of good vs bad. For example, if "crng init done" timestamp is
>>>>>>>> off, put the "tracing_off(); panic();" there. Then grab the serial console
>>>>>>>> output to see what were the last callbacks that was queued/invoked.
>>>>>>
>>>>>> Would you be willing to try these steps? Meanwhile I will try on my side as
>>>>>> well with the .config you sent me in another email.
>>>>>>
>>>>> Not exactly those steps. But see below:
>>>>>
>>>>> <snip>
>>>>> [ 2.291319] e1000 0000:00:03.0 eth0: Intel(R) PRO/1000 Network Connection
>>>>> [ 17.302946] e1000 0000:00:03.0 ens3: renamed from eth0
>>>>> <snip>
>>>>>
>>>>> 15 seconds delay between two prints. I have logged all call_rcu() users
>>>>> between those two prints:
>>>>>
>>>>> <snip>
>>>>> # tracer: nop
>>>>> #
>>>>> # entries-in-buffer/entries-written: 166/166 #P:64
>>>>> #
>>>>> # _-----=> irqs-off/BH-disabled
>>>>> # / _----=> need-resched
>>>>> # | / _---=> hardirq/softirq
>>>>> # || / _--=> preempt-depth
>>>>> # ||| / _-=> migrate-disable
>>>>> # |||| / delay
>>>>> # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
>>>>> # | | | ||||| | |
>>>>> systemd-udevd-669 [002] ..... 2.338739: e1000_probe: Intel(R) PRO/1000 Network Connection
>>>>> systemd-udevd-665 [061] ..... 2.338952: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 2.338962: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-665 [061] ..... 2.338965: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 2.338968: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-665 [061] ..... 2.338987: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-645 [053] ..... 2.338989: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 2.338999: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-645 [053] ..... 2.339002: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 2.339024: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> kworker/0:3-546 [000] d..1. 6.329516: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70effe40a0
>>>>> rcuop/0-17 [000] b.... 6.337320: __call_rcu_common: -> 0x0: exit_creds+0x63/0x70 <- 0x0
>>>>> kworker/38:1-744 [038] d..1. 6.841479: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f97e40a0
>>>>> <...>-739 [035] d..1. 6.841479: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f8be40a0
>>>>> <...>-732 [021] d..1. 6.841486: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f53e40a0
>>>>> kworker/36:1-740 [036] d..1. 6.841487: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f8fe40a0
>>>>> rcuop/21-170 [023] b.... 6.849276: __call_rcu_common: -> 0x0: exit_creds+0x63/0x70 <- 0x0
>>>>> rcuop/38-291 [052] b.... 6.849950: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/38-291 [052] b.... 6.849957: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> kworker/5:1-712 [005] d..1. 7.097392: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f13e40a0
>>>>> kworker/19:1-727 [019] d..1. 7.097392: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f4be40a0
>>>>> <...>-719 [007] d..1. 7.097392: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f1be40a0
>>>>> kworker/13:1-721 [013] d..1. 7.097392: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f33e40a0
>>>>> kworker/52:1-756 [052] d..1. 7.097395: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fcfe40a0
>>>>> kworker/29:1-611 [029] d..1. 7.097395: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f73e40a0
>>>>> <...>-754 [049] d..1. 7.097405: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fc3e40a0
>>>>> kworker/12:1-726 [012] d..1. 7.097405: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f2fe40a0
>>>>> kworker/53:1-710 [053] d..1. 7.097405: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fd3e40a0
>>>>> <...>-762 [061] d..1. 7.097405: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70ff3e40a0
>>>>> <...>-757 [054] d..1. 7.097408: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fd7e40a0
>>>>> kworker/25:1-537 [025] d..1. 7.097408: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f63e40a0
>>>>> <...>-714 [004] d..1. 7.097408: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f0fe40a0
>>>>> <...>-749 [044] d..1. 7.097413: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fafe40a0
>>>>> kworker/51:1-755 [051] d..1. 7.097413: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fcbe40a0
>>>>> <...>-764 [063] d..1. 7.097415: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70ffbe40a0
>>>>> <...>-753 [045] d..1. 7.097416: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fb3e40a0
>>>>> kworker/43:1-748 [043] d..1. 7.097416: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fabe40a0
>>>>> kworker/41:1-747 [041] d..1. 7.097416: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fa3e40a0
>>>>> kworker/57:1-760 [057] d..1. 7.097416: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fe3e40a0
>>>>> <...>-720 [008] d..1. 7.097418: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f1fe40a0
>>>>> kworker/58:1-759 [058] d..1. 7.097421: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fe7e40a0
>>>>> kworker/16:1-728 [016] d..1. 7.097424: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f3fe40a0
>>>>> <...>-722 [010] d..1. 7.097427: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f27e40a0
>>>>> kworker/22:1-733 [022] d..1. 7.097432: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f57e40a0
>>>>> <...>-731 [026] d..1. 7.097432: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f67e40a0
>>>>> <...>-752 [048] d..1. 7.097437: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fbfe40a0
>>>>> kworker/18:0-147 [018] d..1. 7.097437: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f47e40a0
>>>>> kworker/39:1-745 [039] d..1. 7.097437: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f9be40a0
>>>>> <...>-716 [003] d..1. 7.097437: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70f0be40a0
>>>>> <...>-703 [050] d..1. 7.097437: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fc7e40a0
>>>>> kworker/42:1-746 [042] d..1. 7.097444: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70fa7e40a0
>>>>> rcuop/13-113 [013] b.... 7.105592: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/13-113 [013] b.... 7.105595: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/10-92 [040] b.... 7.105608: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/10-92 [040] b.... 7.105610: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/16-135 [023] b.... 7.105613: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/8-78 [039] b.... 7.105636: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/8-78 [039] b.... 7.105640: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/12-106 [040] b.... 7.105651: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/12-106 [040] b.... 7.105652: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/19-156 [000] b.... 7.105727: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/19-156 [000] b.... 7.105730: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/5-56 [058] b.... 7.105808: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/5-56 [058] b.... 7.105814: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/20-163 [023] b.... 17.345648: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/20-163 [023] b.... 17.345655: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/14-120 [013] b.... 17.345675: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/14-120 [013] b.... 17.345681: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/6-63 [013] b.... 17.345714: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/6-63 [013] b.... 17.345715: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/9-85 [000] b.... 17.345753: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/9-85 [000] b.... 17.345758: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/17-142 [000] b.... 17.345775: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/17-142 [000] b.... 17.345776: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/17-142 [000] b.... 17.345777: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/11-99 [000] b.... 17.345810: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/11-99 [000] b.... 17.345811: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/15-127 [013] b.... 17.345832: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/15-127 [013] b.... 17.345834: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/1-28 [000] b.... 17.345834: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/1-28 [000] b.... 17.345835: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/15-127 [013] b.... 17.345835: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> rcuop/15-127 [013] b.... 17.345837: __call_rcu_common: -> 0x0: file_free_rcu+0x32/0x50 <- 0x0
>>>>> systemd-udevd-633 [035] ..... 17.346591: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-633 [035] ..... 17.346609: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-633 [035] ..... 17.346659: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-633 [035] ..... 17.346666: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-669 [002] ..... 17.347573: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> kworker/2:2-769 [002] ..... 17.347659: __call_rcu_common: -> 0x0: __wait_rcu_gp+0xff/0x120 <- 0x0
>>>>> systemd-udevd-675 [012] ..... 17.347981: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-675 [012] ..... 17.348002: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-675 [012] ..... 17.348037: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348098: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348117: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-665 [061] ..... 17.348120: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348156: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348166: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348176: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-642 [050] ..... 17.348179: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348186: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348197: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348200: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348231: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348240: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348250: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348259: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348262: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348305: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348317: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348332: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348336: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348394: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348403: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348406: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 17.348503: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 17.348531: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-645 [053] ..... 17.348535: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348536: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 17.348563: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-665 [061] ..... 17.348575: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348628: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348704: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348828: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348884: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348904: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348954: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348983: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.348993: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349002: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349014: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349024: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349026: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349119: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349182: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349243: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349430: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349462: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349472: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349483: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349486: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349583: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349632: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349666: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349699: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 17.349727: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349733: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 17.349739: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-645 [053] ..... 17.349742: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349765: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-645 [053] ..... 17.349766: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-642 [050] ..... 17.349780: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-665 [061] ..... 17.349800: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-642 [050] ..... 17.349815: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-642 [050] ..... 17.349829: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-642 [050] ..... 17.349832: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349834: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-675 [012] ..... 17.349835: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-675 [012] ..... 17.349853: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-642 [050] ..... 17.349861: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> systemd-udevd-675 [012] ..... 17.349873: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.349879: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.350007: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.350011: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.350080: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.350175: __call_rcu_common: -> ____fput+0x0/0x10: task_work_run+0x5c/0x90 <- 0x0
>>>>> systemd-udevd-665 [061] ..... 17.350362: dev_change_name: --> renamed from eth0
>>>>> <snip>
>>>>>
>>>>> First delay:
>>>>>
>>>>> <snip>
>>>>> systemd-udevd-645 [053] ..... 2.339024: __call_rcu_common: -> 0x0: __dentry_kill+0x140/0x180 <- 0x2
>>>>> kworker/0:3-546 [000] d..1. 6.329516: __call_rcu_common: -> 0x0: queue_rcu_work+0x2b/0x40 <- 0xffff8c70effe40a0
>>>>> <snip>
>>>>>
>>>>> __dentry_kill() function and after 4 seconds there is another one queue_rcu_work().
>>>>> I have checked the __dentry_kill() if it can do any sync talk with RCU but from the
>>>>> first glance i do not see anything critical. But more attention is required.
>>>>
>>>> Can you log rcu_barrier() as well? It could be that the print is just a side
>>>> effect of something else that is not being printed.
>>>>
>>> It has nothing to do with rcu_barrier() in my case. Also i have checked
>>> the synchronize_rcu() it also works as expected, i.e. it is not a
>>> blocking reason.
>>>
>>> Have you tried my config?
>>>
>>> --
>>> Uladzislau Rezki
>> OK. Seems one place i have spot:
>>
>> <snip>
>> [ 7.074847] calling init_sr+0x0/0x1000 [sr_mod] @ 668
>> [ 22.422808] sr 1:0:0:0: [sr0] scsi3-mmc drive: 4x/4x cd/rw xa/form2 tray
>> [ 22.422815] cdrom: Uniform CD-ROM driver Revision: 3.20
>> [ 32.664590] sr 1:0:0:0: Attached scsi CD-ROM sr0
>> [ 32.664642] initcall init_sr+0x0/0x1000 [sr_mod] returned 0 after 25589786 usecs
>> <snip>
>>
>> --
>> Uladzislau Rezki
>
> OK. Found the boot up issue. In my case i had 120 seconds delay:

Wow, nice work.

> <snip>
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 448748e3fba5..a56cfd612e3a 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -312,7 +312,7 @@ void scsi_eh_scmd_add(struct scsi_cmnd *scmd)
> * Ensure that all tasks observe the host state change before the
> * host_failed change.
> */
> - call_rcu(&scmd->rcu, scsi_eh_inc_host_failed);
> + call_rcu_flush(&scmd->rcu, scsi_eh_inc_host_failed);

Great! Thanks. I’ll include this and the other one you converted in the next revision.

Thanks,

- Joel

> }
>
> /**
> <snip>
>
> After this change the boot-up time settles back to normal 4 seconds.
>
> --
> Uladzislau Rezki