rich7420 commented on code in PR #929:
URL: https://github.com/apache/mahout/pull/929#discussion_r2724290189
##########
qdp/qdp-python/src/lib.rs:
##########
@@ -65,6 +64,14 @@ impl QuantumTensor {
return Err(PyRuntimeError::new_err("Invalid DLPack tensor
pointer"));
}
+ if let Some(stream) = stream {
+ if stream > 0 {
+ qdp_core::dlpack::synchronize_stream(stream as *mut
std::ffi::c_void).map_err(
+ |e| PyRuntimeError::new_err(format!("CUDA stream sync
failed: {}", e)),
+ )?;
+ }
+ }
+
Review Comment:
DLPack stream handling treats special CUDA stream values 1 (legacy default)
and 2 (per-thread default) as raw pointers, which can lead to invalid
cudaStream_t usage and undefined behavior. The array API spec explicitly
defines these values as non-pointer sentinel values for CUDA streams. The
current logic calls synchronize_stream for any stream > 0, passing 1/2
directly. I think this should be mapped to cudaStreamLegacy/cudaStreamPerThread
(or avoided) per spec.
ref:
https://data-apis.org/array-api/latest/API_specification/generated/array_api.array.__dlpack__.html
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