[DRBD-user] drbd_flush_workqueue stuck

[RUGINA Szabolcs-Gavril]

Hi folks,
Thank you for your time and support in advance.

We have a problem since a while, and it consumed a lot of time to narrow down the reason.

Our final "catch" is that apparently a DRBD resource is stuck and that causes in cascade other problems.
The setup is:

  *   RHEL cluster, Pacemaker, DRBD
  *   httpd, httpd-fs, httpd-storage (configured as a drbd resource with 2 nodes and a diskless tiebreaker node)

Kernel stack (the problematic one):
[<ffffffffc09ffeb3>] drbd_flush_workqueue+0x63/0x80 [drbd] (<== stuck)
[<ffffffffc09ed2e2>] conn_disconnect+0x102/0x450 [drbd]
[<ffffffffc09ee438>] drbd_receiver+0x1f8/0x780 [drbd]
[<ffffffffc09fc206>] drbd_thread_setup+0xb6/0x1f0 [drbd]
[<ffffffff84ac61f1>] kthread+0xd1/0xe0
[<ffffffff8518dd1d>] ret_from_fork_nospec_begin+0x7/0x21
[<ffffffffffffffff>] 0xffffffffffffffff

Software versions used:
[root at dep-1 myusername]# rpm -qa | grep drbd
kmod-drbd90-9.0.20-1.el7_7.elrepo.x86_64
drbd90-utils-9.12.2-1.el7.elrepo.x86_64
[root at dep-1 myusername]# rpm -qa | grep pacema
pacemaker-libs-1.1.20-5.el7_7.2.x86_64
pacemaker-cli-1.1.20-5.el7_7.2.x86_64
pacemaker-1.1.20-5.el7_7.2.x86_64
pacemaker-cluster-libs-1.1.20-5.el7_7.2.x86_64
[root at dep-1 myusername]# rpm -qa | grep corosync
corosync-2.4.3-6.el7_7.1.x86_64
corosync-qdevice-2.4.3-6.el7_7.1.x86_64
corosynclib-2.4.3-6.el7_7.1.x86_64
[root at dep-1 frqadmin]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.7 (Maipo)

Resource config attached: drbd-resource-conf.txt.
Stack for all threads attached: drbd-resource-full-stack.txt.

Do you have any idea what could be wrong, what is causing the thread to stuck?

Best Regards,
Szabi.

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