我启动了mysqld并反复停止了它，以便在不同的配置下运行一些测试。但是，有时会发生以下情况。
请查看以下命令以解决该问题：
[root@hhc S1_auto-test]# ps aux | grep mysql
root 336 0.0 0.0 113312 1640 ? S Jun14 0:00 /bin/sh /usr/local/mysql/bin/mysqld_safe --query-prealloc-size=16384 --innodb-log-file-size=200M --max-connections=2000
mysql 574 0.1 7.2 2661360 583760 ? Sl Jun14 1:35 /usr/local/mysql/bin/mysqld --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data --plugin-dir=/usr/localmysql/lib/plugin --user=mysql --query-prealloc-size=16384 --innodb-log-file-size=200M --max-connections=2000 --log-error=hhc.err --pid-file=hhc.pid --socket=/var/lib/mysql/mysql.sock
[root@hhc S1_auto-test]# kill 336 547
-bash: kill: (547) - No such process
[root@hhc S1_auto-test]# find / -name mysql.sock
[root@hhc S1_auto-test]#
[root@hhc S1_auto-test]# ps aux | grep mysql
root 336 0.0 0.0 113312 1640 ? S Jun14 0:00 /bin/sh /usr/local/mysql/bin/mysqld_safe --query-prealloc-size=16384 --innodb-log-file-size=200M --max-connections=2000
mysql 574 0.1 7.2 2661360 583760 ? Sl Jun14 1:35 /usr/local/mysql/bin/mysqld --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data --plugin-dir=/usr/localmysql/lib/plugin --user=mysql --query-prealloc-size=16384 --innodb-log-file-size=200M --max-connections=2000 --log-error=hhc.err --pid-file=hhc.pid --socket=/var/lib/mysql/mysql.sock
检查/usr/local/mysql/data/hhc.err：
2019-06-14T04:47:30.355313Z 0 [Note] --secure-file-priv is set to NULL. Operations related to importing and exporting data are disabled
2019-06-14T04:47:30.355354Z 0 [Note] /usr/local/mysql/bin/mysqld (mysqld 5.7.25) starting as process 574 ...
2019-06-14T04:47:30.363191Z 0 [Note] InnoDB: PUNCH HOLE support available
2019-06-14T04:47:30.363230Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2019-06-14T04:47:30.363237Z 0 [Note] InnoDB: Uses event mutexes
2019-06-14T04:47:30.363242Z 0 [Note] InnoDB: GCC builtin __sync_synchronize() is used for memory barrier
2019-06-14T04:47:30.363248Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.11
2019-06-14T04:47:30.363253Z 0 [Note] InnoDB: Using Linux native AIO
2019-06-14T04:47:30.365108Z 0 [Note] InnoDB: Number of pools: 1
2019-06-14T04:47:30.365299Z 0 [Note] InnoDB: Using CPU crc32 instructions
2019-06-14T04:47:30.367955Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2019-06-14T04:47:30.378910Z 0 [Note] InnoDB: Completed initialization of buffer pool
2019-06-14T04:47:30.382551Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
2019-06-14T04:47:30.394813Z 0 [Note] InnoDB: Highest supported file format is Barracuda.
2019-06-14T04:47:30.407915Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables
2019-06-14T04:47:30.407961Z 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
2019-06-14T04:47:30.507913Z 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
2019-06-14T04:47:30.508673Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.
2019-06-14T04:47:30.508688Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.
2019-06-14T04:47:30.509773Z 0 [Note] InnoDB: Waiting for purge to start
2019-06-14T04:47:30.559921Z 0 [Note] InnoDB: 5.7.25 started; log sequence number 168133946
2019-06-14T04:47:30.560079Z 0 [Note] InnoDB: Loading buffer pool(s) from /mnt/mysql-5.7.25/data/ib_buffer_pool
2019-06-14T04:47:30.560347Z 0 [Note] Plugin 'FEDERATED' is disabled.
2019-06-14T04:47:30.564917Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without certificate and private key
2019-06-14T04:47:30.565152Z 0 [Note] Server hostname (bind-address): '*'; port: 3306
2019-06-14T04:47:30.565214Z 0 [Note] IPv6 is available.
2019-06-14T04:47:30.565230Z 0 [Note] - '::' resolves to '::';
2019-06-14T04:47:30.565254Z 0 [Note] Server socket created on IP: '::'.
2019-06-14T04:47:30.577697Z 0 [Note] /usr/local/mysql/bin/mysqld: ready for connections.
Version: '5.7.25' socket: '/var/lib/mysql/mysql.sock' port: 3306 MySQL Community Server (GPL)
2019-06-14T04:47:30.586070Z 0 [Note] InnoDB: Buffer pool(s) load completed at 190614 12:47:30
2019-06-14T04:47:47.031917Z 0 [Note] Giving 0 client threads a chance to die gracefully
2019-06-14T04:47:47.031949Z 0 [Note] Shutting down slave threads
2019-06-14T04:47:47.031961Z 0 [Note] Forcefully disconnecting 0 remaining clients
我知道kill -9可以最终杀死mysqld进程。但是我只想知道为什么会这样，hhc.err的最后三行是什么原因。