I've got a Dell XPS 13 9370 with Ubuntu 18.10. When I close the lid, the laptop suspends, but after a few seconds I can see the display lighting up again. If I leave it closed for half an hour, I can feel it getting hot. Also, the battery is drained while being suspended.
As far as I can read from the syslog, it's making the same suspend loop over and over. In 30 minutes, it's looping through the following activity:
Apr 4 10:10:16 rossy wpa_supplicant[1444]: nl80211: deinit ifname=wlp2s0 disabled_11b_rates=0
Apr 4 10:10:16 rossy kernel: [67470.354441] Restarting tasks ... done.
Apr 4 10:10:16 rossy systemd-sleep[16878]: System resumed.
Apr 4 10:10:16 rossy kernel: [67470.511487] PM: suspend exit
------------------------------
Apr 4 10:10:17 rossy systemd[1]: Started Suspend.
Apr 4 10:10:17 rossy systemd[1]: sleep.target: Unit not needed anymore. Stopping.
Apr 4 10:10:17 rossy systemd[1]: Stopped target Sleep.
Apr 4 10:10:17 rossy systemd[1]: Reached target Suspend.
Apr 4 10:10:17 rossy systemd[1]: suspend.target: Unit not needed anymore. Stopping.
Apr 4 10:10:17 rossy systemd[1]: Stopped target Suspend.
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.0053] manager: sleep: wake requested (sleeping: yes enabled: yes)
Apr 4 10:10:17 rossy kernel: [67470.526314] IPv6: ADDRCONF(NETDEV_UP): wlp2s0: link is not ready
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.0054] device (wlp2s0): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'managed')
Apr 4 10:10:17 rossy /usr/lib/gdm3/gdm-x-session[2806]: (II) event13 - ELAN24EE:00 04F3:24EE: is tagged by udev as: Touchscreen
Apr 4 10:10:17 rossy /usr/lib/gdm3/gdm-x-session[2806]: (II) event13 - ELAN24EE:00 04F3:24EE: device is a touch device
Apr 4 10:10:17 rossy kernel: [67471.266359] ath10k_pci 0000:02:00.0: Unknown eventid: 118809
Apr 4 10:10:17 rossy kernel: [67471.269386] ath10k_pci 0000:02:00.0: Unknown eventid: 90118
Apr 4 10:10:17 rossy kernel: [67471.313317] IPv6: ADDRCONF(NETDEV_UP): wlp2s0: link is not ready
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.7951] device (B4:8B:19:6B:0E:38): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'managed')
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.7973] manager: NetworkManager state is now CONNECTED_LOCAL
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.7982] device (B4:8B:19:6B:0E:38): state change: unavailable -> disconnected (reason 'none', sys-iface-state: 'managed')
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.8845] sup-iface[0x55a937c35c20,wlp2s0]: supports 5 scan SSIDs
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.8865] device (wlp2s0): supplicant interface state: starting -> ready
Apr 4 10:10:17 rossy NetworkManager[1433]: <info> [1554365417.8867] device (wlp2s0): state change: unavailable -> disconnected (reason 'supplicant-available', sys-iface-state: 'managed')
Apr 4 10:10:17 rossy kernel: [67471.408313] IPv6: ADDRCONF(NETDEV_UP): wlp2s0: link is not ready
Apr 4 10:10:19 rossy ModemManager[1411]: <info> Couldn't check support for device '/sys/devices/pci0000:00/0000:00:1c.2/0000:02:00.0': not supported by any plugin
Apr 4 10:10:32 rossy /usr/lib/gdm3/gdm-x-session[2806]: (II) event13 - ELAN24EE:00 04F3:24EE: device removed
Apr 4 10:10:34 rossy ModemManager[1411]: <info> [device /sys/devices/pci0000:00/0000:00:14.0/usb1/1-10] creating modem with plugin 'Generic' and '1' ports
Apr 4 10:10:34 rossy ModemManager[1411]: <warn> Could not grab port (tty/ttyACM0): 'Cannot add port 'tty/ttyACM0', unhandled serial type'
Apr 4 10:10:34 rossy ModemManager[1411]: <warn> Couldn't create modem for device '/sys/devices/pci0000:00/0000:00:14.0/usb1/1-10': Failed to find primary AT port
Apr 4 10:10:40 rossy gsd-power[2522]: Error setting property 'PowerSaveMode' on interface org.gnome.Mutter.DisplayConfig: Tijd is verlopen (g-io-error-quark, 24)
Apr 4 10:10:42 rossy gsd-power[2522]: Error setting property 'PowerSaveMode' on interface org.gnome.Mutter.DisplayConfig: Tijd is verlopen (g-io-error-quark, 24)
Apr 4 10:10:46 rossy NetworkManager[1433]: <info> [1554365446.0703] manager: sleep: sleep requested (sleeping: no enabled: yes)
Apr 4 10:10:46 rossy NetworkManager[1433]: <info> [1554365446.0705] device (wlp2s0): state change: disconnected -> unmanaged (reason 'sleeping', sys-iface-state: 'managed')
Apr 4 10:10:46 rossy NetworkManager[1433]: <info> [1554365446.0797] device (B4:8B:19:6B:0E:38): state change: disconnected -> unmanaged (reason 'sleeping', sys-iface-state: 'managed')
Apr 4 10:10:46 rossy NetworkManager[1433]: <info> [1554365446.0816] manager: NetworkManager state is now ASLEEP
Apr 4 10:10:46 rossy wpa_supplicant[1444]: nl80211: deinit ifname=p2p-dev-wlp2s0 disabled_11b_rates=0
Apr 4 10:10:46 rossy systemd[1]: Reached target Sleep.
Apr 4 10:10:46 rossy systemd[1]: Starting Suspend...
Apr 4 10:10:46 rossy systemd-sleep[16960]: Suspending system...
Apr 4 10:10:46 rossy kernel: [67499.633833] PM: suspend entry (s2idle)
Apr 4 10:10:46 rossy kernel: [67499.633835] PM: Syncing filesystems ... done.
Apr 4 10:10:46 rossy kernel: [67499.643953] Freezing user space processes ... (elapsed 0.092 seconds) done.
Apr 4 10:10:46 rossy kernel: [67499.736513] OOM killer disabled.
Apr 4 10:10:46 rossy kernel: [67499.736514] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
Apr 4 10:10:46 rossy kernel: [67499.738396] Suspending console(s) (use no_console_suspend to debug)
Apr 4 10:10:46 rossy kernel: [67500.434487] OOM killer enabled.
Apr 4 10:10:46 rossy wpa_supplicant[1444]: nl80211: deinit ifname=wlp2s0 disabled_11b_rates=0
Apr 4 10:10:46 rossy kernel: [67500.434489] Restarting tasks ... done.
Apr 4 10:10:47 rossy systemd-sleep[16960]: System resumed.
Apr 4 10:10:47 rossy kernel: [67500.559340] PM: suspend exit
------------------------------
Apr 4 10:10:47 rossy systemd[1]: Started Suspend.
Apr 4 10:10:47 rossy systemd[1]: sleep.target: Unit not needed anymore. Stopping.
Apr 4 10:10:47 rossy systemd[1]: Stopped target Sleep.
Apr 4 10:10:47 rossy systemd[1]: Reached target Suspend.
Here is some system info (lspci):
00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers (rev 08)
00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (rev 07)
00:04.0 Signal processing controller: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor Thermal Subsystem (rev 08)
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
00:15.0 Signal processing controller: Intel Corporation Sunrise Point-LP Serial IO I2C Controller #0 (rev 21)
00:15.1 Signal processing controller: Intel Corporation Sunrise Point-LP Serial IO I2C Controller #1 (rev 21)
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI #1 (rev 21)
00:1c.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #1 (rev f1)
00:1c.2 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #3 (rev f1)
00:1c.4 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #5 (rev f1)
00:1d.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #9 (rev f1)
00:1f.0 ISA bridge: Intel Corporation Intel(R) 100 Series Chipset Family LPC Controller/eSPI Controller - 9D4E (rev 21)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
01:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS525A PCI Express Card Reader (rev 01)
02:00.0 Network controller: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter (rev 32)
03:00.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
04:00.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
04:01.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
04:02.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
04:04.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
39:00.0 USB controller: Intel Corporation JHL6540 Thunderbolt 3 USB Controller (C step) [Alpine Ridge 4C 2016] (rev 02)
6e:00.0 Non-Volatile memory controller: SK hynix Device 1527
Putting the laptop in airplane mode or disabling Bluetooth seems to fix this issue.