Re: PROBLEM: I/O system call never returns if file desc is closed

[Alexander Viro]

On 7 Jun 2001, Florian Weimer wrote:

> There's a subtle difference: For malloc(), libc has a mutex (or
> whatever), but for open(), socket() etc., no locking is performed, and
> many libc functions create (and destroy) descriptors imlicitely.  

So? You don't have to close() descriptors you had not (to your code
knowledge) opened. End of story.

> I still don't see how you can write maintainable and reliable software
> with asynchronous close().  For example, if some select() call returns
> EBADF after an asynchronous close(), you would have to scan the
> descriptors to find the offending one, but in the meantime, it has
> been reused by another thread.  What do you do in this case?

You don't rely on EBADF. It's _your_ code that had closed the thing. Unless
you pass descriptors of unknown origin into select() (hardly a good idea)
you have all information you need to provide an exclusion.