Re: cache problem

[Olly Betts]

On 2008-10-17, Eric Blake <address@hidden> wrote:
> According to Olly Betts on 10/16/2008 7:40 PM:
>> On 2008-10-16, Ralf Wildenhues <address@hidden> wrote:
>>> How do you get two concurrent configure scripts updating the same
>>> config.cache file?
>> 
>> Open terminal (or screen) windows for two subdirectories of the combined
>> tree and in each modify a file which causes configure to be rerun (e.g.
>> Makefile.am if using automake) and then run "make".
>
> Well, given that we now have documentation of use case, maybe it's worth
> revisiting Ralf's patch.  Are you comfortable testing it out on top of the
> current state of the git repository?

I'm comfortable, but I'm not sure it would achieve much - I've never
actually noticed a problem in practice, even though there's clearly a
theoretical problem with the setup I use if the cache file isn't updated
atomically.

It seems that this would be really hard to actually make happen on
demand since you have to get the execution of

    cat confcache >$cache_file
    
near the end of each configure script to overlap in time, and each takes
a tiny fraction of a second whereas the rest of the script takes several
seconds.

Cheers,
    Olly