develoment workflow: how to avoid duplicate work ?

[valdis.kletnieks at vt.edu]

On Mon, 04 Jun 2018 18:31:31 -0400, Hugo Lefeuvre said:

> Do you mean that the ioctl/read/write call increments the reference
> count in this case ? It would mean that these syscalls aren't really
> using passed FD but instead create duplicates to make sure the open
> file description won't be freed during their execution, right ?

One file descriptor is passed around, and each syscall or other code that needs
to protect it from evaporating out from under it takes a reference.  Think of
it as "How many of you are still using it? 3? OK.. I won't clean up yet. Oh,
it's down to zero? OK, it's clean up time"

Another example of the same sort of thing can be seen in file systems, where
one or more file descriptors can be opened on a given file, and the file is
then unlinked - but the inode and the allocated space doesn't actually get
freed until all the open descriptors (each of which increments the ref count)
are closed and the refcount actually reaches zero.  That's what's going on when
you run 'lsof' and see files listed as '(deleted)', or when you *think* you've
cleaned up the logs, but /var is still sitting at 98%....


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