[arch-general] System Freeze on sleep

Prateek Sadhukhan psadhukh at gmail.com
Mon May 31 05:23:07 UTC 2021

This is interesting. I will store this in my notes too. The issue is I am
working on a laptop and so dont have a serial port.

But I think I have found the problem. I am soaking it for now, I will respond
to the thread if my hunch works.


Sefa Eyeoglu via arch-general <arch-general at lists.archlinux.org> writes:

> I recently had a similar issue.
> As it was breaking my workflow for day-to-day use I investigated the issue.
> If the computer is unresposive while resuming it's very likely to be a kernel 
> panic.
> If there is no display output at all, either the graphics driver itself causes 
> the panic, or some kernel module before that.
> The only way to debug these kinds of kernel panics was to use a serial port 
> and a second computer to get a tty.
> As most computers have a COM-header on the mainboard, it's fairly easy to get 
> things connected.
> I purchased a COM-RS232 PCIe Shield and found a Serial to USB adapter at home.
> I then set the following kernel cmdline
> 	no_console_suspend console=tty0 console=ttyS0,115200
> no_console_suspend was needed in my case, but it might not be needed in all 
> cases, I am sure it's not recommended to always have that enabled, but as we 
> are debugging here we should be fine.
> The two console= arguments set the console (kernel log, systemd log and 
> panics) to both tty0 (the default) as well as ttyS0 at a baud of 115200 (Check 
> if ttyS0 is your serial port while booted).
> Now you can get your USB-Serial adapter, connect it with your computer's COM 
> port and start a serial console like screen, minicom or picocom.
> Now you should see the kernel log while booting. You can even have getty on 
> there to login via serial. (I don't know right now if it is autostarted or if 
> you need to start it manually with systemctl start getty at ttyS0.service)
> Now you can get to debugging: Reproduce your issue and see what you get there.
> P.S.
> There are other ways to see the console without working graphics. There is 
> USB-3.0 debugging (couldn't get that to work myself) and netconsole (didn't 
> work for my issue, maybe it wasn't initialised before the panic)
> P.S.P.S.
> I planned to write this process up somewhere, I guess having it here is a 
> start. I may create a Wiki article about this in the future.
> P.S.P.S.P.S.
> My issue was an actual kernel bug, which I fixed and got merged with recent 
> 5.11 and 5.12 releases. See https://git.kernel.org/pub/scm/linux/kernel/git/
> torvalds/linux.git/commit/?id=7df4ceb60fa9a3c5160cfd5b696657291934a2c9
>> Hello All,
>> After upgrading to the new kernel I see that my system freezes when
>> I try to resume from sleep. This happens intermittently but frequent enough
>> to be irritating. I have to reboot the system to recover.
>> I am running kernel 5.12.7-arch1-1
>> The issue was not seen with kernel 5.11.
>> I am running arch on btrfs and I suspect it is a btrfs issue somehow. When I
>> check dmesg (journactl --dmesg --boot -1) I see that it always ends with
>> the following two lines when the issue is seen.
>> May 29 07:12:40 matrix kernel: PM: suspend entry (deep)
>> May 29 07:12:40 matrix kernel: Filesystems sync: 0.025 seconds
>> I wanted to know how do I attempt to debug this issue?
>> Regards,
>> Prateek

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