kernel filesystem sync hung suspend for ~70 seconds while leaving the screen in a half-enabled state

[matte-schwartz]

Your system information

• Steam client version: 172368248
• SteamOS version: 3.6.10
• Opted into Steam client beta?: Yes
• Opted into SteamOS beta?: Yes
• Have you checked for updates in Settings > System?: Yes
• SteamOS System Report - njtransit215 (8/16/2024)

Please describe your issue in as much detail as possible:

I had my Steam Deck appear to hang during suspend for around a minute while the screen was in a half-enabled "zombie" state, half-dimmed with mangohud frozen at the top. dmesg logs looked pretty normal apart from this ~70 second filesystem sync. I'm including a dump of my Steam logs pulled from the devkit client here, although nothing there looked that suspicious to me:
logs.tar.gz

None of the mangohud information actually changed while frozen like this.

Aug 16 19:03:49 steamdeck kernel: PM: suspend entry (deep)
Aug 16 19:03:55 steamdeck systemd-resolved[557]: Switching to fallback DNS server 1.1.1.1#cloudflare-dns.com.
Aug 16 19:03:58 steamdeck systemd[1]: NetworkManager-dispatcher.service: Deactivated successfully.
Aug 16 19:04:58 steamdeck kernel: Filesystems sync: 69.233 seconds

This issue appears to be sporadic. It may even be a one off, but I wasn't finding any matching reports here by searching "suspend" so I figured I'd file a System Report right after it happened.

Steps for reproducing this issue:

1. Exit playing a game, and wait long enough for all user-facing sync operations to appear like they've finished (like game downloads or Steam cloud syncing). Make sure mangohud is enabled.
2. Suspend the unit with the top button
3. Observe the unit (maybe?) fail to go to sleep for a somewhat extended period of time.