Document fsession deadline regression test

src/52-fsession-latency/README.md

@@ -172,7 +172,7 @@ The repository uses bpftool v7.7.0, whose nested libbpf is v1.7.0. libbpf 1.7.0
 
 ## Running the Tests
 
-The integration test runs three scenarios against the built binary:
+The integration test runs four scenarios against the built binary:
 
 ```bash
 sudo make test
@@ -183,6 +183,7 @@ The test validates:
 1. An unmatched PID (2^32 - 1) produces zero calls, proving the TGID filter works.
 2. A 10-second threshold (10,000,000 us) produces no slow events even though reads complete, proving the threshold comparison works.
 3. A 10 ms threshold with a pipe read delayed by 50 ms produces at least one slow event, proving the end-to-end reporting path works.
+4. Threshold 0 with continuous target-TGID reads through the one-second deadline produces calls and events, and the CLI still exits successfully. This protects the normal-success exit path when the final `ring_buffer__poll()` call consumes events.
 
 ## Requirements
 

src/52-fsession-latency/README.zh.md

@@ -172,7 +172,7 @@ extern __u64 *bpf_session_cookie(void *ctx) __ksym;
 
 ## 运行测试
 
-集成测试对构建产物运行三个场景：
+集成测试对构建产物运行四个场景：
 
 ```bash
 sudo make test
@@ -183,6 +183,7 @@ sudo make test
 1. 不匹配的 PID (2^32 - 1) 产生零次调用，证明 TGID 过滤器有效。
 2. 10 秒阈值 (10,000,000 us) 即使有读操作完成也不产生慢事件，证明阈值比较逻辑正确。
 3. 10 ms 阈值加上延迟 50 ms 的管道读产生至少一个慢事件，证明端到端上报路径正常工作。
+4. 阈值为 0 时，持续对目标 TGID 执行读操作直到一秒截止时间结束，产生调用和事件，且 CLI 仍然成功退出。该场景保护最后一次 `ring_buffer__poll()` 消费事件后的正常退出路径。
 
 ## 环境要求