Repeated kernel hangs on 2.6.32-220.2.1.el6: umount stuck in synchronize_sched_expedited for 9 hours

Solution Verified - Updated -

Issue

  • NFS umount stuck in synchronize_sched_expedited() for 9 hours.
  • Using sysrq to trigger a core dump and examining the core shows the the NFS umount process stuck with a backtrace similar to the following
PID: 31208  TASK: ffff88063b78cac0  CPU: 0   COMMAND: "umount"
 #0 [ffff8805f4313b48] schedule at ffffffff814eca93
 #1 [ffff8805f4313c10] schedule_timeout at ffffffff814ed985
 #2 [ffff8805f4313cc0] wait_for_common at ffffffff814ed603
 #3 [ffff8805f4313d50] wait_for_completion at ffffffff814ed71d
 #4 [ffff8805f4313d60] synchronize_sched_expedited at ffffffff81062f51
 #5 [ffff8805f4313dc0] synchronize_rcu_expedited at ffffffff810ddc7e
 #6 [ffff8805f4313dd0] bdi_remove_from_list at ffffffff811340ea
 #7 [ffff8805f4313df0] bdi_unregister at ffffffff811341b1
 #8 [ffff8805f4313e20] nfs_put_super at ffffffffa04899e9 [nfs]
 #9 [ffff8805f4313e30] generic_shutdown_super at ffffffff8117864b
#10 [ffff8805f4313e50] kill_anon_super at ffffffff81178736
#11 [ffff8805f4313e70] nfs_kill_super at ffffffffa048c415 [nfs]
#12 [ffff8805f4313e90] deactivate_super at ffffffff811796c0
#13 [ffff8805f4313eb0] mntput_no_expire at ffffffff8119563f
#14 [ffff8805f4313ee0] sys_umount at ffffffff811960db

Environment

  • Red Hat Enterprise Linux 6
    • kernels prior to 2.6.32-358.el6
    • seen on 2.6.32-220.2.1.el6

Subscriber exclusive content

A Red Hat subscription provides unlimited access to our knowledgebase of over 48,000 articles and solutions.

Current Customers and Partners

Log in for full access

Log In
Close

Welcome! Check out the Getting Started with Red Hat page for quick tours and guides for common tasks.