How to troubleshoot suspend and hibernate in Ubuntu

Some tips are at https://wiki.ubuntu.com/DebuggingKernelSuspendHibernateResume

Fails to suspend/hibernate

$ dmesg|less

There is usually an entry what application caused the suspension to fail:

[32467.560058] Freezing of tasks failed after 20.01 seconds (1 tasks refusing to freeze, wq_busy=0):
[32467.560115] plasma-desktop D 0000000000000000 0 2065 1 0x00800004
...

The stack trace often tells you where the problem might lie:

[32467.560155] [<ffffffff81087f00>] ? autoremove_wake_function+0x0/0x40
[32467.560163] [<ffffffffa016e523>] SendReceive+0x1a3/0x3b0 [cifs]
[32467.560169] [<ffffffffa0153c79>] CIFSSMBUnixQPathInfo+0x139/0x2b0 [cifs]
[32467.560176] [<ffffffffa016853d>] cifs_get_inode_info_unix+0x7d/0x1a0

• here it is the CIFS (samba) mounts.

Fail to resume

Make sure the swap partition is correctly set, see https://help.ubuntu.com/community/SwapFaq