cudaErrorInvalidSyncObject (806) cuda runtime_error ai_generated true

CUDA error: invalid sync object (cudaErrorInvalidSyncObject)

ID: cuda/cuda-error-invalid-sync-object

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80%Fix Rate
86%Confidence
1Evidence
2025-06-18First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
CUDA 12.5 active — — —
CUDA 12.7 active — — —
NVIDIA Driver 560.35.03 active — — —
NVIDIA Driver 565.57.01 active — — —
PyTorch 2.6.0 active — — —

Root Cause

A CUDA synchronization object (e.g., cudaExternalSemaphore or cudaEvent) was passed to an API that expects a valid, initialized object, but the object was destroyed, never created, or created on a different device context.

generic

中文

向期望有效、已初始化对象的 API 传递了 CUDA 同步对象（例如 cudaExternalSemaphore 或 cudaEvent），但该对象已被销毁、从未创建或在不同的设备上下文中创建。

Official Documentation

https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__TYPES.html

Workarounds

  1. 85% success Verify that the sync object is created on the correct device context. For example, in CUDA C++: `cudaSetDevice(deviceId); cudaEvent_t event; cudaEventCreate(&event);` Ensure all subsequent uses of `event` are on the same device. 
    Verify that the sync object is created on the correct device context. For example, in CUDA C++: `cudaSetDevice(deviceId); cudaEvent_t event; cudaEventCreate(&event);` Ensure all subsequent uses of `event` are on the same device.
  2. 80% success Check if the sync object has been destroyed before reuse. Implement a wrapper that tracks the object's lifetime: `if (event) { cudaEventDestroy(event); event = nullptr; }` 
    Check if the sync object has been destroyed before reuse. Implement a wrapper that tracks the object's lifetime: `if (event) { cudaEventDestroy(event); event = nullptr; }`
  3. 75% success For external semaphores, ensure the import handle is valid and the driver supports the semaphore type. Use `cudaImportExternalSemaphore` with a properly initialized `cudaExternalSemaphoreHandleDesc`. 
    For external semaphores, ensure the import handle is valid and the driver supports the semaphore type. Use `cudaImportExternalSemaphore` with a properly initialized `cudaExternalSemaphoreHandleDesc`.

中文步骤

  1. Verify that the sync object is created on the correct device context. For example, in CUDA C++: `cudaSetDevice(deviceId); cudaEvent_t event; cudaEventCreate(&event);` Ensure all subsequent uses of `event` are on the same device.
  2. Check if the sync object has been destroyed before reuse. Implement a wrapper that tracks the object's lifetime: `if (event) { cudaEventDestroy(event); event = nullptr; }`
  3. For external semaphores, ensure the import handle is valid and the driver supports the semaphore type. Use `cudaImportExternalSemaphore` with a properly initialized `cudaExternalSemaphoreHandleDesc`.

Dead Ends

Common approaches that don't work:

  1. 70% fail

    Synchronizing the device does not recreate or validate the sync object; it only waits for pending operations to complete.

  2. 85% fail

    The error is about an invalid object handle, not resource exhaustion; more streams do not fix a null or cross-context object.