tugot17 opened a new pull request, #644:
URL: https://github.com/apache/tvm-ffi/pull/644
## Problem
The prebuilt torch C-DLPack addon is cached under a filename derived only
from torch **major.minor** + a coarse device string:
```python
major, minor = torch.__version__.split(".")[:2]
device = _torch_extension_device(torch) # "cuda" / "rocm" / "cpu"
libname = f"libtorch_c_dlpack_addon_torch{major}{minor}-{device}{suffix}"
lib_path = cache_dir / libname # cache_dir defaults to
~/.cache/tvm-ffi
if not lib_path.exists():
...build... # otherwise reuse whatever
is there
```
This key omits:
- the torch **patch** version (`2.9.0` vs `2.9.1`),
- the build local-version tag carried in `torch.__version__` (`+cu121` vs
`+cu124`, `+cpu`, …),
- the C++ ABI flag (`torch._C._GLIBCXX_USE_CXX11_ABI`).
Since the addon is a compiled extension linking libtorch's C++ ABI, two
torch installs that share `major.minor` + device but differ in patch / CUDA
toolkit / ABI resolve to the **same** cached `.so`. The addon built against the
first torch is then silently reused by the second — an ABI mismatch in the
DLPack bridge that surfaces as crashes, memory faults, or **silently wrong
tensor data**, not a clean error.
This is easy to hit whenever `~/.cache/tvm-ffi` is shared across
environments — a shared/NFS home, or container images that mount the host home
and see the same cache under different torch builds.
## Reproduce
```bash
# env A
pip install torch==2.9.0+cu121 --index-url
https://download.pytorch.org/whl/cu121
python -c "import tvm_ffi" # builds
~/.cache/tvm-ffi/libtorch_c_dlpack_addon_torch29-cuda.so
# env B: same major.minor, different build/ABI, same cache dir
pip install torch==2.9.1+cu124 --index-url
https://download.pytorch.org/whl/cu124
python -c "import tvm_ffi" # REUSES the cu121-built torch29-cuda.so ->
ABI mismatch
```
The same applies to any two builds that share
`torch{major}{minor}-{device}`, including CPU and ROCm builds.
## Fix
Fold the full torch build identity (`torch.__version__`, which already
carries patch + `+cuXXX`/`+rocmX.Y`/`+cpu`) and the C++ ABI flag into the
cached addon name via a short hash. Incompatible builds now get distinct cache
entries, while same-build reuse is unchanged. The build subprocess receives
`libname` from this call site, so it stays consistent automatically.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
