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fix(attention): remove stale barrier_O arrive in empty-tile fast path #13

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Merged
fdz-1999 merged 1 commit into from
Aug 18, 2026
Merged

fix(attention): remove stale barrier_O arrive in empty-tile fast path #13

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11 changes: 0 additions & 11 deletions include/flashinfer/attention/hopper/prefill_sm90.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -243,17 +243,6 @@ __global__ void __launch_bounds__(Ktraits::NUM_WARPS* cutlass::NumThreadsPerWarp
int num_kv_tiles = collective_mainloop.get_num_kv_tiles(mainloop_params, q_tile_idx, qo_len,
kv_len, batch_idx);
if (num_kv_tiles <= 0) { // We exit early and write 0 to gO and -inf to gLSE.
// Preserve producer/consumer barrier parity when skipping this tile.
// A following visible tile would otherwise wait on a missing arrival.
if (work_idx != 0) {
int lane_predicate = cute::elect_one_sync();
if (cutlass::canonical_warp_idx_sync() == Ktraits::NUM_WARPS - 1 && lane_predicate) {
#pragma unroll
for (uint32_t cta_id = 0; cta_id < 1; ++cta_id) {
shared_storage.barrier_O.arrive(cta_id, lane_predicate);
}
}
}
collective_epilogue.store_zero(epilogue_params, shared_storage,
threadIdx.x - NUM_COPY_THREADS, block_coord);
continue;
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