It is interesting how a user-space task could lead to hinder a Linux kernel software suspend operation.

[11735.155443] PM: suspend entry (deep)
[11735.155445] PM: Syncing filesystems ... done.
[11735.215091] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
[11735.215172] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
[11735.558676] rfkill: input handler enabled
[11735.608859] (NULL device *): firmware: direct-loading firmware rtlwifi/rtl8723befw_36.bin
[11735.609910] (NULL device *): firmware: direct-loading firmware rtl_bt/rtl8723b_fw.bin
[11735.611871] Freezing user space processes ... 
[11755.615603] Freezing of tasks failed after 20.003 seconds (1 tasks refusing to freeze, wq_busy=0):
[11755.615854] digikam         D    0 13262  13245 0x00000004
[11755.615859] Call Trace:
[11755.615873]  __schedule+0x28e/0x880
[11755.615878]  schedule+0x2c/0x80
[11755.615889]  request_wait_answer+0xa3/0x220 [fuse]
[11755.615895]  ? finish_wait+0x80/0x80
[11755.615902]  __fuse_request_send+0x86/0x90 [fuse]
[11755.615907]  fuse_request_send+0x27/0x30 [fuse]
[11755.615914]  fuse_send_readpages.isra.30+0xd1/0x120 [fuse]
[11755.615920]  fuse_readpages+0xfd/0x110 [fuse]
[11755.615928]  __do_page_cache_readahead+0x200/0x2d0
[11755.615936]  filemap_fault+0x37b/0x640
[11755.615940]  ? filemap_fault+0x37b/0x640
[11755.615944]  ? filemap_map_pages+0x179/0x320
[11755.615950]  __do_fault+0x1e/0xb0
[11755.615953]  __handle_mm_fault+0xc8a/0x1160
[11755.615958]  handle_mm_fault+0xb1/0x200
[11755.615964]  __do_page_fault+0x257/0x4d0
[11755.615968]  do_page_fault+0x2e/0xd0
[11755.615973]  page_fault+0x22/0x30
[11755.615976] RIP: 0033:0x7f32d3c7ff90
[11755.615978] RSP: 002b:00007ffd887c9d18 EFLAGS: 00010246
[11755.615981] RAX: 00007f32d3fc9c50 RBX: 000000000275e440 RCX: 0000000000000003
[11755.615982] RDX: 0000000000000002 RSI: 00007ffd887c9f10 RDI: 000000000275e440
[11755.615984] RBP: 00007ffd887c9f10 R08: 000000000275e820 R09: 00000000018d2f40
[11755.615986] R10: 0000000000000002 R11: 0000000000000000 R12: 000000000189cbc0
[11755.615987] R13: 0000000001839dc0 R14: 000000000275e440 R15: 0000000000000000
[11755.616014] OOM killer enabled.
[11755.616015] Restarting tasks ... done.
[11755.817640] PM: suspend exit
[11755.817698] PM: suspend entry (s2idle)
[11755.817700] PM: Syncing filesystems ... done.
[11755.983156] rfkill: input handler disabled
[11756.030209] rfkill: input handler enabled
[11756.073529] Freezing user space processes ... 
[11776.084309] Freezing of tasks failed after 20.010 seconds (2 tasks refusing to freeze, wq_busy=0):
[11776.084630] digikam         D    0 13262  13245 0x00000004
[11776.084636] Call Trace:
[11776.084653]  __schedule+0x28e/0x880
[11776.084659]  schedule+0x2c/0x80
[11776.084672]  request_wait_answer+0xa3/0x220 [fuse]
[11776.084680]  ? finish_wait+0x80/0x80
[11776.084688]  __fuse_request_send+0x86/0x90 [fuse]
[11776.084695]  fuse_request_send+0x27/0x30 [fuse]
[11776.084703]  fuse_send_readpages.isra.30+0xd1/0x120 [fuse]
[11776.084711]  fuse_readpages+0xfd/0x110 [fuse]
[11776.084721]  __do_page_cache_readahead+0x200/0x2d0
[11776.084730]  filemap_fault+0x37b/0x640
[11776.084735]  ? filemap_fault+0x37b/0x640
[11776.084743]  ? __update_load_avg_blocked_se.isra.33+0xa1/0xf0
[11776.084749]  ? filemap_map_pages+0x179/0x320
[11776.084755]  __do_fault+0x1e/0xb0
[11776.084759]  __handle_mm_fault+0xc8a/0x1160
[11776.084765]  handle_mm_fault+0xb1/0x200
[11776.084772]  __do_page_fault+0x257/0x4d0
[11776.084777]  do_page_fault+0x2e/0xd0
[11776.084783]  page_fault+0x22/0x30
[11776.084787] RIP: 0033:0x7f31ddf315e0
[11776.084789] RSP: 002b:00007ffd887ca068 EFLAGS: 00010202
[11776.084793] RAX: 00007f31de13c350 RBX: 00000000040be3f0 RCX: 000000000283da60
[11776.084795] RDX: 0000000000000001 RSI: 00000000040be3f0 RDI: 00000000040be3f0
[11776.084797] RBP: 00007f32d3fca1e0 R08: 0000000005679250 R09: 0000000000000020
[11776.084799] R10: 00000000058fc1b0 R11: 0000000004b9ac50 R12: 0000000000000000
[11776.084801] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
[11776.084806] QXcbEventReader D    0 13268  13245 0x00000004
[11776.084810] Call Trace:
[11776.084817]  __schedule+0x28e/0x880
[11776.084823]  schedule+0x2c/0x80
[11776.084827]  rwsem_down_write_failed_killable+0x25a/0x490
[11776.084832]  call_rwsem_down_write_failed_killable+0x17/0x30
[11776.084836]  ? call_rwsem_down_write_failed_killable+0x17/0x30
[11776.084842]  down_write_killable+0x2d/0x50
[11776.084848]  do_mprotect_pkey+0xa9/0x2f0
[11776.084854]  SyS_mprotect+0x13/0x20
[11776.084859]  system_call_fast_compare_end+0xc/0x97
[11776.084861] RIP: 0033:0x7f32d1f7c057
[11776.084863] RSP: 002b:00007f32cbb8c8d8 EFLAGS: 00000206 ORIG_RAX: 000000000000000a
[11776.084867] RAX: ffffffffffffffda RBX: 00007f32c4000020 RCX: 00007f32d1f7c057
[11776.084869] RDX: 0000000000000003 RSI: 0000000000001000 RDI: 00007f32c4024000
[11776.084871] RBP: 00000000000000c5 R08: 00007f32c4000000 R09: 0000000000024000
[11776.084872] R10: 00007f32c4024000 R11: 0000000000000206 R12: 00000000000000a0
[11776.084874] R13: 00007f32c4022f60 R14: 0000000000001000 R15: 00000000000000e0
[11776.084906] OOM killer enabled.
[11776.084907] Restarting tasks ... done.
[11776.289655] PM: suspend exit
[11776.459624] IPv6: ADDRCONF(NETDEV_UP): wlp1s0: link is not ready
[11776.469521] rfkill: input handler disabled
[11776.978733] IPv6: ADDRCONF(NETDEV_UP): wlp1s0: link is not ready
[11777.038879] IPv6: ADDRCONF(NETDEV_UP): wlp1s0: link is not ready
[11778.022062] wlp1s0: authenticate with 50:8f:4c:82:4d:dd
[11778.033155] wlp1s0: send auth to 50:8f:4c:82:4d:dd (try 1/3)
[11778.038522] wlp1s0: authenticated
[11778.041511] wlp1s0: associate with 50:8f:4c:82:4d:dd (try 1/3)
[11778.059860] wlp1s0: RX AssocResp from 50:8f:4c:82:4d:dd (capab=0x431 status=0 aid=5)
[11778.060253] wlp1s0: associated
[11778.060308] IPv6: ADDRCONF(NETDEV_CHANGE): wlp1s0: link becomes ready
[11778.987669] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
[11779.117608] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
[11779.160930] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
[11779.784045] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
[11779.913668] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
[11779.961517] [drm:wait_panel_status [i915]] *ERROR* PPS state mismatch
11:58 ♒♒♒   ☺