Re: closefd: closes a file of any process

Hi Tigran!

On Tue, Jun 27, 2000 at 02:24:09PM +0100, Tigran Aivazian wrote:
> On Tue, 27 Jun 2000 [e-mail] wrote:
> > __but__ filp calls locs_wake_up_blocks __always__ with wait = 0
> > 
> > so it seems there is no a problem here
> 
> well spotted! Ok then, I agree the Linux locks implementation is not as
> broken as I thought :)

I hope you also agree with me that lock_kernel() is enoght to protect the
files_struct on a 2.2.x kernel

> Amazing that nobody noticed this before. Ok, next problem - how do you 
> synchronize this non-current do_close() with the possibility of the
> process being between
> 
> file = fget(fd);
> ...
> fput(file);

In 2.2.x kernels seems that all functions that use these construction use
lock_kernel(), so it seems my module is correct now? remember is for 2.2.x
(please check the new version at the same URL)

In 2.3.x kernels... Is very different fget|fput has they own locks... 

> ? You can add a rw semaphore to struct file, being taken read inside fget
> and write in (only non-current!) do_close but that means such do_close can
> potentially be blocked forever (if someone is doing a read() that can
> block forever, e.g. on /proc/kmsg). So, we may need interruptible
> read-write semaphores?
> 
> What think ye?

let me think on it...

regards
		Ulisses

                Debian/GNU Linux: a dream come true
-----------------------------------------------------------------------------
"Computers are useless. They can only give answers."            Pablo Picasso

--->	Visita http://www.valux.org/ para saber acerca de la	<---
--->	Asociación Valenciana de Usuarios de Linux		<---