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Date: Sat, 18 Jun 2022 01:28:49 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Steven Rostedt <rostedt@...dmis.org>
CC: LKML <linux-kernel@...r.kernel.org>
Subject: Re: possible trace_printk() bug in v5.19-rc1
> On Jun 17, 2022, at 3:50 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Thu, 16 Jun 2022 15:36:43 +0000
> Chuck Lever III <chuck.lever@...cle.com> wrote:
>
>>> Did you remove any modules before displaying the trace?
>>
>> I haven't explicitly removed nfsd.ko, and lsmod says it's still there.
>> And, trace_printk was working as expected on v5.18.
>
> Are you sure?
Yes, I'm sure. I just checked out v5.18 and built it with the
same CONFIG. trace_printk() on that kernel generates function
names as expected.
> I just checkout v5.19-rc2 and added the below patch. Then I did the
> following:
>
> # rmmod bridge
>
> # trace-cmd start -p function -l :mod:bridge
>
> # insmod bridge
>
> # trace-cmd show
> # tracer: function
> #
> # entries-in-buffer/entries-written: 23/23 #P:8
> #
> # _-----=> irqs-off/BH-disabled
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / _-=> migrate-disable
> # |||| / delay
> # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
> # | | | ||||| | |
> modprobe-2155 [005] ...1. 4732.051406: br_init <-do_one_initcall
> modprobe-2155 [005] ..... 4732.051408: br_init: here in bridge
> modprobe-2155 [005] ...1. 4732.051408: br_fdb_init <-br_init
> modprobe-2155 [005] ...1. 4732.051418: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051418: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051418: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051418: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051418: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051419: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051419: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051419: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051419: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051419: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051419: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051420: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051420: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051420: br_device_event <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: br_device_event: this is an event
> modprobe-2155 [005] ...1. 4732.051421: br_netlink_init <-br_init
> modprobe-2155 [005] ...1. 4732.051421: br_mdb_init <-br_netlink_init
>
> # rmmod bridge
>
> # trace-cmd show
> # tracer: function
> #
> # entries-in-buffer/entries-written: 56/56 #P:8
> #
> # _-----=> irqs-off/BH-disabled
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / _-=> migrate-disable
> # |||| / delay
> # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
> # | | | ||||| | |
> modprobe-2155 [005] ...1. 4732.051406: 0xffffffffc0cc7000 <-do_one_initcall
> modprobe-2155 [005] ..... 4732.051408: 0xffffffffc0cc702b: here in bridge
> modprobe-2155 [005] ...1. 4732.051408: 0xffffffffc0cc7101 <-0xffffffffc0cc7043
> modprobe-2155 [005] ...1. 4732.051418: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051418: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051418: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051418: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051418: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051419: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051419: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051419: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051419: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051419: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051419: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051420: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051420: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051420: 0xffffffffc0d81340 <-call_netdevice_register_net_notifiers
> modprobe-2155 [005] ..... 4732.051420: 0xffffffffc0d81345: this is an event
> modprobe-2155 [005] ...1. 4732.051421: 0xffffffffc0cc7132 <-0xffffffffc0cc70a3
> modprobe-2155 [005] ...1. 4732.051421: 0xffffffffc0da1500 <-0xffffffffc0cc713e
> kworker/u16:2-2023 [004] ...1. 4737.946576: 0xffffffffc0d81340 <-raw_notifier_call_chain
> kworker/u16:2-2023 [004] ..... 4737.946578: 0xffffffffc0d81345: this is an event
> kworker/u16:2-2023 [004] ...1. 4737.946634: 0xffffffffc0d8e1a0 <-if_nlmsg_size
> kworker/u16:2-2023 [004] ...1. 4737.946735: 0xffffffffc0d81340 <-raw_notifier_call_chain
> kworker/u16:2-2023 [004] ..... 4737.946735: 0xffffffffc0d81345: this is an event
> kworker/u16:2-2023 [004] ...1. 4737.946833: 0xffffffffc0d81340 <-raw_notifier_call_chain
> kworker/u16:2-2023 [004] ..... 4737.946833: 0xffffffffc0d81345: this is an event
> kworker/u16:2-2023 [004] ...1. 4737.946834: 0xffffffffc0d8e1a0 <-if_nlmsg_size
> kworker/u16:2-2023 [004] ...1. 4737.957648: 0xffffffffc0d81190 <-cleanup_net
> rmmod-2206 [000] ...1. 5739.459376: 0xffffffffc0d8f880 <-0xffffffffc0da3d1d
> rmmod-2206 [000] ...1. 5739.459378: 0xffffffffc0da1570 <-0xffffffffc0d8f88a
> rmmod-2206 [000] ...1. 5739.471367: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471368: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471369: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471369: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471369: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471369: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471370: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471370: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471370: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471370: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471370: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471370: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471371: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471371: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471371: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471371: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471371: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471372: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.471372: 0xffffffffc0d81340 <-call_netdevice_unregister_notifiers
> rmmod-2206 [000] ..... 5739.471372: 0xffffffffc0d81345: this is an event
> rmmod-2206 [000] ...1. 5739.477366: 0xffffffffc0d81190 <-unregister_pernet_operations
> rmmod-2206 [000] ...1. 5739.477375: 0xffffffffc0d84910 <-__do_sys_delete_module.constprop.0
>
> Before removing the module, the names were all present. Then after I
> removed the module, they did not exist.
>
> Other than that, I cannot reproduce the issue.
>
> -- Steve
>
>
> diff --git a/net/bridge/br.c b/net/bridge/br.c
> index 96e91d69a9a8..4067760d3763 100644
> --- a/net/bridge/br.c
> +++ b/net/bridge/br.c
> @@ -36,6 +36,7 @@ static int br_device_event(struct notifier_block *unused, unsigned long event, v
> bool changed_addr;
> int err;
>
> + trace_printk("this is an event\n");
> if (netif_is_bridge_master(dev)) {
> err = br_vlan_bridge_event(dev, event, ptr);
> if (err)
> @@ -385,6 +386,7 @@ static int __init br_init(void)
> return err;
> }
>
> + trace_printk("here in bridge\n");
> err = br_fdb_init();
> if (err)
> goto err_out;
--
Chuck Lever
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