当执行 nginx -s reload 之后.
会发现 旧的nginx worker process 进程已经标记为 shutting down。
新的worker process 也已经成功启动。但是旧的shutting down进行一直存在，没有退出。
14 root 0:00 nginx: master process /usr/local/nginx/sbin/nginx
15 root 0:00 nginx: worker process is shutting down
16 root 0:00 nginx: worker process is shutting down
17 root 0:00 nginx: worker process is shutting down
18 root 0:00 nginx: worker process is shutting down
32 root 0:00 nginx: worker process is shutting down
33 root 0:00 nginx: worker process is shutting down
34 root 0:00 nginx: worker process is shutting down
35 root 0:00 nginx: worker process is shutting down
57 root 0:00 nginx: worker process is shutting down
58 root 0:00 nginx: worker process is shutting down
59 root 0:00 nginx: worker process is shutting down
60 root 0:00 nginx: worker process is shutting down
114 root 0:00 nginx: worker process is shutting down
115 root 0:00 nginx: worker process is shutting down
116 root 0:00 nginx: worker process is shutting down
117 root 0:00 nginx: worker process is shutting down
123 root 0:00 nginx: worker process is shutting down
124 root 0:00 nginx: worker process is shutting down
125 root 0:00 nginx: worker process is shutting down
126 root 0:00 nginx: worker process is shutting down
190 root 0:00 nginx: worker process is shutting down
191 root 0:00 nginx: worker process is shutting down
192 root 0:00 nginx: worker process is shutting down
193 root 0:00 nginx: worker process is shutting down
197 root 0:00 nginx: worker process
198 root 0:00 nginx: worker process
199 root 0:00 nginx: worker process
200 root 0:00 nginx: worker process
当执行 nginx -s reload 之后.
会发现 旧的nginx worker process 进程已经标记为 shutting down。
新的worker process 也已经成功启动。但是旧的shutting down进行一直存在，没有退出。