[Bug Fix] Fix some bugs

[ming1753]

Motivation

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Modifications

Usage or Command

Accuracy Tests

Checklist

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[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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[fastdeploy-bot]

🤖 AI Code Review | 2026-04-08 11:08 CST

📋 Review 摘要

PR 概述：修复 GPU 算子中的同步问题和边界条件 bug

变更范围：custom_ops/gpu_ops/append_attn/、custom_ops/gpu_ops/flash_mask_attn/

影响面 Tag：[OP]

📝 PR 规范检查

PR 标题和描述存在以下问题：

1. 标题 Tag 格式不正确：[Bug Fix] 应改为 [BugFix]（官方 Tag 列表中无空格）
2. 描述部分未填写：Motivation 和 Modifications 部分为空

标题建议（可直接复制）：

• [BugFix] Fix some bugs

描述模板（可直接复制）：

## Motivation
修复了以下 bug：
1. get_block_shape_and_split_kv_block.cu 中条件编译结构错误导致代码分支不正确
2. flash_mask_attn 中当 seq_len_k 不是 kBlockN 整数倍时可能读取未初始化的 shared memory

## Modifications
1. 修复 get_block_shape_and_split_kv_block.cu 中的条件编译结构，并添加 cudaStreamSynchronize 确保 DtoH copy 完成后再读取
2. 在 flash_mask_attn mainloop 中添加边界检查，清零最后一个 block 中无效的 V 数据

问题

未发现阻塞性问题。代码修复逻辑正确，但建议完善测试覆盖。

总体评价

代码修复正确，逻辑合理。两个 bug 修复都是必要的：

1. 条件编译修复解决了编译分支错误
2. 边界检查和清零避免了读取未初始化 shared memory 的潜在问题

建议完善 PR 描述并考虑补充边界条件测试。

[fastdeploy-bot]

🟡 建议 原代码中 #endif 位置不正确，导致条件编译结构错误。修复后代码逻辑正确，建议在 commit message 中说明此问题的影响。