Question about cache flushing and fork

[Randolph Chung <randolph@tausq.org>]

Hi,

Can someone please explain why it is necessary to flush the cache 
during fork()? (i.e. call to flush_cache_mm() in dup_mmap)

It seems that after fork, the parent and child have access to the same
vm, so it should be sufficient to flush the tlb, and create two pte's
for the processes. I can see that during COW processing there can be
kernel/user cache aliasing issues on virtually indexed caches, but
that seems to be taken care of by copy_cow_page(). 

I've read through cachetlb.txt, but it just says:

        This interface is used to handle whole address space
        page table operations such as what happens during
        fork, exit, and exec.

I can see why this is needed for exit(), but why fork()? and i don't see
this used for exec() ?

Also is there an updated version of the "Linux Cache Flush Architecture"
document? (http://en.tldp.org/LDP/khg/HyperNews/get/memory/flush.html)
This is a very nicely written doc, but it seems a bit out of date for
2.6 (e.g. flush_page_to_ram is gone)

thanks
randolph
-- 
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/