Linux系统数据库最近老是被自动停止，请看下面数据库日志，求解

180903 15:15:05 [Note] /phpstudy/mysql/bin/mysqld: Normal shutdown
180903 15:15:05 [Note] Event Scheduler: Purging the queue. 0 events
180903 15:15:06 mysqld_safe A mysqld process already exists
180903 15:15:07 [Warning] /phpstudy/mysql/bin/mysqld: Forcing close of thread 168914 user: 'root'
180903 15:15:07 InnoDB: Starting shutdown...
180903 15:15:08 InnoDB: Shutdown completed; log sequence number 36066475
180903 15:15:08 [Note] /phpstudy/mysql/bin/mysqld: Shutdown complete
180903 15:15:08 mysqld_safe mysqld from pid file /phpstudy/data/izwz96j9cwd5tkq1spg0kkz.pid ended