c - POSIX 文件锁是否可重入？

Question

我正在通过 fcntl 使用 POSIX mandatory 文件锁。我想知道这些锁是否可重入，即。进程能否获取它已经拥有的锁？

Answer 1

通过fcntl 的建议锁是基于每个进程的，并且只是在给定进程的文件上累积锁定间隔。也就是说，由应用程序来跟踪时间间隔，任何针对某个时间间隔的解锁调用都会解锁它，而不管针对该时间间隔进行了多少次锁定调用。

更糟糕的是，关闭该文件的任何文件描述符都会取消对该文件的所有锁定:

As well as being removed by an explicit F_UNLCK, record locks are automatically released when the process terminates or if it closes any file descriptor referring to a file on which locks are held. This is bad: it means that a process can lose the locks on a file like /etc/passwd or /etc/mtab when for some reason a library function decides to open, read and close it.