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I know this error has been had by many people, but I couldn't find any examples of it happening routinely on a specific day of the week. It caused Ubuntu to freeze.

failed command: READ FPDMA QUEUED

This only ever happens on Tuesday for me, several times in the morning, usually about 10-20 minutes after booting, and after 2-3 forced shutdowns, it eventually stops, until next week.

I've had a look in the crontab for anything, but I'm not sure what to look for.

For comments:

$ systemctl list-timers
Tue 2018-08-14 06:23:06 BST  14h left      Mon 2018-08-13 09:31:04 BST  6h ago    apt-daily-upgrade.timer      apt-daily-upgrade.ser
Tue 2018-08-14 09:45:46 BST  17h left      Mon 2018-08-13 09:45:46 BST  6h ago    systemd-tmpfiles-clean.timer systemd-tmpfiles-clea

$ ls -al /etc/cron.weekly/fstrim
-rwxr-xr-x 1 root root 86 Apr 13  2016 /etc/cron.weekly/fstrim

$ cat /etc/crontab | grep weekly
47 6    * * 7   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )

Kernel logs

/var/log/kern.log.1:80:Aug  7 09:44:42 pc kernel: [  707.304054] ata7.00: failed command: READ FPDMA QUEUED
/var/log/kern.log.1:107:Aug  7 09:45:15 pc kernel: [  740.071623] ata7.00: failed command: READ FPDMA QUEUED
/var/log/kern.log.1:111:Aug  7 09:45:15 pc kernel: [  740.071665] ata7.00: failed command: READ FPDMA QUEUED
/var/log/kern.log.1:126:Aug  7 09:45:47 pc kernel: [  772.838856] ata7.00: failed command: READ FPDMA QUEUED
Flosculus
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  • If it is planned, then it may be caused by Cron or SystemD timers. I think it is TRIM-related. Please add output of systemctl list-timers, ls -al /etc/cron.weekly/fstrim and cat /etc/crontab | grep weekly. – N0rbert Aug 07 '18 at 09:57
  • @N0rbert added. – Flosculus Aug 13 '18 at 15:23
  • I do not see any clues about Tuesday. Try to search /var/log for occurencies of READ FPDMA QUEUED. – N0rbert Aug 13 '18 at 16:19
  • @N0rbert i've added the logs, and before it just happened, i went into the F2 terminal a waited for it to happen, then ran top and there was fstrim. – Flosculus Aug 14 '18 at 08:56
  • Just curious what is your SSD model? And does it support TRIM on hardware level? Please add output of sudo hdparm -I /dev/sda | grep TRIM (change /dev/sda to the appropriate rootfs device) to the question. And check this paragraph. – N0rbert Aug 14 '18 at 09:36

1 Answers1

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As we have discovered that the issue is caused by fstrim, let's disable it:

sudo rm /etc/cron.weekly/fstrim

And then see how system works after disabling TRIM.

Note: my system is installed on Samsung PRO SSD. 

$ sudo hdparm -I /dev/sda | grep TRIM
   *    Data Set Management TRIM supported (limit 8 blocks)
   *    Deterministic read ZEROs after TRIM

I have both periodic TRIM (fstrim cron-job) and continuous TRIM (discard option in /etc/fstab). It operates without issues.

N0rbert
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