linux-kernel - Re: Fwd: [6.5.1] Slow boot and opening files (RIP: kvfree_rcu

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Message-ID: <ZPXyUTteVxXtqiEo@pc636>
Date:   Mon, 4 Sep 2023 17:05:53 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Marcus Seyfarth <m.seyfarth@...il.com>
Cc:     Uladzislau Rezki <urezki@...il.com>, paulmck@...nel.org,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Ziwei Dai <ziwei.dai@...soc.com>, linux-kernel@...r.kernel.org,
        rcu@...r.kernel.org
Subject: Re: Fwd: [6.5.1] Slow boot and opening files (RIP: kvfree_rcu_bulk)

>     Could you please clarify some items:
> 
>     1.
>     <snip>
>     if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) {
>             debug_rcu_bhead_unqueue(bnode);
>             rcu_lock_acquire(&rcu_callback_map);
>     <snip>
> 
>     Do you see this warning? I mean the one that is in the if()?
> 
> 
> Hi! From my limited understanding, the warning points to that snippet: [  
>  7.108424] WARNING: CPU: 13 PID: 338 at kernel/rcu/tree.c:2952
> kvfree_rcu_bulk+0x13b/0x160
> 
OK. Since you have a compiled vmlinux. Just to be sure, could you please
perform below steps:

<snip>
urezki@...38:~/data/raid0/coding/linux.git$ gdb ./vmlinux
GNU gdb (Debian 10.1-1.7) 10.1.90.20210103-git
Copyright (C) 2021 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./vmlinux...
(gdb) l *kvfree_rcu_bulk+0x13b
<snip>

and post the output here?

>
> I also don't get that warning any longer in my experiments when overwriting /
> kernel/rcu/tree.c with the file from 6.4.14.
>  
The 6.4 does not have such warnings, therefore you do not see it :)

> 
>     2. Please provide a full .config file.
>     3. Could you please also to be more specific how to reproduce a boot delay
>     and the warning you see?
>     4. Please provide your full dmesg.
> 
> 
> The boot delay and warnings happen with both my self-compiled 6.5.1 and the
> CachyOS default Kernel 6.5.0-2. Reproducing is as simple as booting into that
> system and open up dmesg after the task bar eventually shows up (which takes 10
> - 20 seconds longer than normal). The warning goes away when overwriting /
> kernel/rcu/tree.c with the file from 6.4.14. But the slow boot, task bar and
> the shutdown/reboot problem remained. Journalctl signals some failures with
> powerdevil that do not happen with the older Kernel installed.
> 
Let's focus on your own self compiled kernel. As for the 6.5.1 kernel,
could you please point your SHA1 so i can take a vanilla kernel and base
my testing on exactly the same baseline?


> I've attached the files to this mail for convenience. 
> 
Appreciate and thank you for the help!

--
Uladzislau Rezki