Fix cudaErrorPeerAccessAlreadyEnabled: P2P Already Active

Overview

cudaErrorPeerAccessAlreadyEnabled occurs when calling cudaDeviceEnablePeerAccess for a GPU pair that already has P2P enabled.

Error Messages

CUDA error: peer access already enabled
cudaErrorPeerAccessAlreadyEnabled

Common Causes

• •Calling EnablePeerAccess twice
• •Not tracking P2P state
• •Multiple initialization paths

Solutions

static bool p2pEnabled[8][8] = {false};
if (!p2pEnabled[dev0][dev1]) {
    cudaDeviceEnablePeerAccess(dev1, 0);
    p2pEnabled[dev0][dev1] = true;
}

cudaError_t err = cudaDeviceEnablePeerAccess(dev, 0);
if (err != cudaSuccess && err != cudaErrorPeerAccessAlreadyEnabled) {
    // Handle real error
}

Prevention Tips

• ✓Initialize P2P once at startup
• ✓Track enabled state

Code Examples

Before (Problematic)

Enabling twice.

cudaDeviceEnablePeerAccess(1, 0);
cudaDeviceEnablePeerAccess(1, 0);  // Error!

After (Fixed)

Guard against duplicate calls.

if (!p2pEnabled) {
    cudaDeviceEnablePeerAccess(1, 0);
    p2pEnabled = true;
}

Frequently Asked Questions

Related Errors

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