Compatibility Report

Game: Assassin's Creed Shadows (AppID: 3159330)
Proton version(s) tested: Experimental, 11.0 (Beta), GE-Proton 11-1
Distro: Arch Linux
Kernel: 7.0.9-arch2-1
GPU: NVIDIA GeForce RTX 5070 Max-Q (Blackwell GB206M)
Driver: nvidia-open-dkms 595.71.05

Symptoms

The game freezes in specific areas (e.g., the arena). It is a game-only freeze — the window is still responsive, can alt-tab, and the process can be killed. The freeze is consistently reproducible in these areas.

Debugging

The freeze is caused by a userspace deadlock in the game's job/task system. One TaskThread worker thread spins at 30-60% CPU in RtlAcquireSRWLockExclusive / RtlReleaseSRWLockExclusive with wchan: 0 (no kernel wait — pure userspace spin). All other TaskThreads sleep on futex or ntsync.

Thread states during freeze (example):

  TID  STATE  WCHAN                       COMM
  93763 S     ntsync_schedule.isra.0      TaskThread00
  93765 R     (running, wchan: 0)          TaskThread02   ← spinning thread
  93764 S     ntsync_schedule.isra.0      TaskThread01
  93766 S     ntsync_schedule.isra.0      TaskThread03
  ...

GDB backtrace of the spinning thread:

#0  RtlAcquireSRWLockExclusive () from ntdll.dll
#1  RtlReleaseSRWLockExclusive () from ntdll.dll

Attempted Workarounds (all fail)

Notes

• No Xid errors, no GPU driver crashes in dmesg/journalctl
• The game runs fine on Windows 11 with the same settings on this hardware
• The issue manifests specifically in high-density areas (arena) where the task scheduler generates more jobs
• 95 threads total, 10 TaskThread workers spawned (scales with CPU count)
• Appears to be a Wine SRW lock fairness/implementation bug, not a GPU driver or game data issue