Fix cudaErrorPrimaryContextActive: Context Already Retained

Overview

cudaErrorPrimaryContextActive occurs when modifying context flags after context is active.

Error Messages

CUDA error: primary context active
cudaErrorPrimaryContextActive

Common Causes

• •Setting flags after CUDA call
• •Context already created
• •Wrong init order

Solutions

cudaSetDeviceFlags(cudaDeviceScheduleBlockingSync);  // FIRST
cudaSetDevice(0);

Prevention Tips

• ✓Set flags at program start
• ✓Before cudaMalloc/cudaSetDevice

Code Examples

Before (Problematic)

Context active.

cudaSetDevice(0);
cudaSetDeviceFlags(flags);  // Too late!

After (Fixed)

Flags first.

cudaSetDeviceFlags(flags);
cudaSetDevice(0);

Frequently Asked Questions

Related Errors

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