Re: dlopen/dlclose behaviour - real reloading from disk required.

[Charles Coldwell <coldwell at gmail dot com>]

On Dec 9, 2009, at 2:47 PM, PrzemysÅaw Firszt wrote:

> Hi,
> I'm working on an input driver for xorg. Xorg server uses dlopen/ 
> dlclose
> from glibc to load module driver. I want to modify/update to driver
> module without shutting down xorg.
>
> Currently situation looks like that:
> 1. xorg started
> 2. load the input driver module (using whole xorg mechanism, but it  
> goes
> down to dlopen)
> 3. test the driver
> 4. unload the driver module (as above, but dlclose)
> 5. modify the driver
> 6. reinstall the driver module (or remove from disk/reinstall -  
> doesn't
> make any difference)
> 7. load the input driver
> I'm expecting to see _new_ version of the driver loaded at point 7,  
> but
> instead the old version is loaded.


So, in general if a file is unlinked in the filesystem by one process  
while another one still has it open, the associated pages remain in  
the page cache and the blocks continue to be allocated in the  
filesystem until the last process with an open file descriptor on  
that file has closed it.  I wonder if the xorg server continues to  
hold an open file descriptor on the driver file after the dlclose?

--

Charles M. Coldwell, W1CMC
"Turn on, log in, tune out"
Somerville, Massachusetts, New England (FN42kj)

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