[Bug 59838] New: NtSetContextThread access violation in fiber/coroutine init — Path of Exile 2, Intel Arc B580 (xe driver)

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59838

            Bug ID: 59838
           Summary: NtSetContextThread access violation in fiber/coroutine
                    init — Path of Exile 2, Intel Arc B580 (xe driver)
           Product: Wine
           Version: unspecified
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: major
          Priority: P2
         Component: ntdll
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 81127
  --> http://bugs.winehq.org/attachment.cgi?id=81127
Steam log file

# Bug Report: NtSetContextThread access violation with Path of Exile 2 on Intel
Arc B580 (Battlemage / xe driver)

## Summary

Path of Exile 2 deadlocks on startup due to an access violation in
`NtSetContextThread` under all tested Proton and Wine builds. The crash is
consistent and reproducible across five Proton variants, two kernel versions,
with and without the Steam Linux Runtime (pressure-vessel), and across both
available renderers (Vulkan and DX12). The issue appears specific to the Intel
Arc B580 (Battlemage / Xe2) using the `xe` DRM driver. The game works on
Windows on the same hardware.

---

## Environment

| Component | Details |
|---|---|
| OS | Kubuntu 26.04 LTS (Resolute Raccoon) |
| Kernel (tested) | 6.17.0-29-generic, 7.0.0-22-generic — both affected
identically |
| CPU | Intel Core i5-12600KF (Alder Lake, 10-core) |
| GPU | Intel Arc B580 (Battlemage, Xe2) — `Device: Intel Battlemage G21 [Arc
B580], driver: xe` |
| Mesa | 26.0.5 (kisak-mesa PPA) |
| Vulkan | 1.4.341, driver: intel (ANV) |
| Display | Wayland (KDE Plasma / kwin_wayland) |
| RAM | 32 GiB |
| ptrace_scope | Tested at both 1 (default) and 0 — no difference |
| Steam Runtime | Tested with and without (`STEAM_LINUX_RUNTIME=0`) — no
difference |

---

## Proton / Wine Versions Tested

All of the following crash at `NtSetContextThread` with identical or
near-identical register states:

- GE-Proton10-34
- GE-Proton9-27
- Proton Experimental
- Proton Hotfix
- Proton-CachyOS 11.0-20260521 (x86_64_v3)

GE-Proton builds show a slightly earlier crash point (Wine ntdll execute-mutex
initialization); all Valve and CachyOS builds crash consistently at
`NtSetContextThread + 0x25d` / `+ 0x288`.

---

## Crash Description

Path of Exile 2 uses a fiber/coroutine-based job system (GGG's internal engine)
that calls `NtSetContextThread` to switch execution contexts between worker
fibers at startup. Wine's implementation sends a signal to the target thread to
modify its context. This fails on the Intel Arc B580 / xe driver combination,
triggering the game's built-in deadlock detector.

The access violation occurs at `NtSetContextThread + 0x25d` (or `+0x288` in
CachyOS build) reading from address `0x34` (near-null dereference). A secondary
fault then occurs during stack unwind at offset `-0x28` from an invalid
pointer, producing "Fault during unwind" and leaving the thread in a permanent
hang.


---

## Variables Confirmed to Have No Effect

- Kernel version (6.17.0-29 vs 7.0.0-22)
- `STEAM_LINUX_RUNTIME=0` (bypassing pressure-vessel)
- `PROTON_USE_NTSYNC=1` (ntsync loaded via `modprobe ntsync`)
- `ANV_ENABLE_PIPELINE_CACHE=0`
- `PROTON_FORCE_LARGE_ADDRESS_AWARE=1`
- `PROTON_ENABLE_WAYLAND=1`
- `LD_PRELOAD=""`
- `kernel.yama.ptrace_scope=0`
- Renderer: Vulkan vs DirectX 12 (DX12 crashes earlier in a different mutex
init path; Vulkan reaches `NtSetContextThread`)
- Fresh Wine prefix vs existing
- Proton version (see list above)

---

## Additional Notes

- The game runs correctly on Windows 11 on the same hardware (confirmed)
- Other Linux users with NVIDIA or AMD GPUs report the game working normally
under Proton
- Intel Arc B580 uses the `xe` DRM driver (not `i915`); Battlemage (Xe2) is not
supported by `i915`
- The crash occurs during fiber/thread pool initialization before any rendering
begins, making it renderer-independent in practice
- GE-Proton builds (9 and 10) show a related but earlier crash variant in
Wine's ntdll execute-mutex path (`rdx=5f6574756365784d` = "Mxecute_")
suggesting the fiber thread pool init fails at multiple points depending on
Wine version

---

## Steps to Reproduce

1. Install Path of Exile 2 via Steam on a system with Intel Arc B580 (xe
driver) running Linux
2. Set any Proton compatibility tool (GE, Experimental, CachyOS)
3. Launch the game
4. Observe black screen followed by game's DeadlockDetector dialog
5. Run: `cat ~/steam-2694490.log | grep -i
"NtSetContextThread\|deadlock\|fault"` to confirm crash location

---

## Expected Behavior

Game initializes fiber/thread pool and reaches the main menu.

## Actual Behavior

`NtSetContextThread` access violation during fiber context initialization.
Game's DeadlockDetector fires. Process remains alive but hung.

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