Ubuntu – System responds with “failed to send h2c command” on shutdown: what does that mean

18.04driverskernelnetworkingshutdown

Observations

Every so often I notice this message on the terminal when shutting down my computer: failed to send h2c command. I think it hapens every time actually, repeating in some cases. I checked journalctl (is that the kernel/OS logs?) when dealing with another, possibly related issue trying to get mysql to work, and I saw quite a few repeated lines of:

Mar 16 12:41:02 Ethan-TUF kernel: rtw_pci 0000:04:00.0: failed to send h2c command
Mar 16 12:41:04 Ethan-TUF kernel: rtw_pci 0000:04:00.0: failed to send h2c command
Mar 16 12:41:06 Ethan-TUF kernel: rtw_pci 0000:04:00.0: failed to send h2c command

repeating every 2 seconds about 40 times in a row around 12:41 PM, which is I think one of the times I rebooted my computer that day. This message seems to show up whenever I turn off my computer, and a few times it has made shutdowns inconceivably long for an Ubuntu system, but not every time.

Hypothesis And Stuff I've Tried

The only thing I could find in a search about it was this page on Bugzilla. I could not make heads or tails of it, but I understood a few words, which led me to believe the following:

I am assuming it might have something to do with the network card. I have a laptop, an ASUS TUF Gaming FX505DU with a dual boot: the included hard drive for Windows, and another hard drive for Ubuntu 18.04 LTS. I noticed that in the Windows environment, I have an issue where the network adapter routinely stops working during my sessions, and the only way to fix it is to disable and reenable the adapter via the control panel (or the Windows network troubleshooter). I have tried downloading the latest drivers from ASUS themselves, and made sure Windows was up to date. I have also eliminated the possibilities of my WiFi router or anything external being the culprit. I think there may be something wrong with the firmware or the driver, or even faulty hardware or a cable not properly plugged in inside my machine from when it was manufactured, though I have not noticed any interruptions of network communication with the WiFi router during my Ubuntu sessions.

Plea For Help

Am I on the right track? is this a network card issue? and is there any way I could fix or at least understand what is going on? I only sorta know what I'm doing, no clue what h2c means or anything and duckduckgo turned up very little. I appreciate any help!

Best Answer

  • rtw_pci is Realtek's wireless driver rtw88.

    h2c stands for "host to card".

    "failed to send h2c command" suggests that there might be some issue with firmware, but since you are not facing any network issues on Ubuntu and only seeing these messages during shutdown, I think it can be a driver issue as well.

    You should file a bug for this at launchpad. Here is a guide for doing that: https://help.ubuntu.com/community/ReportingBugs

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