On Mon, 28 Jan 2002, Rick Stevens wrote:
> Daniel Phillips wrote:
> [snip]
[page table COW description]
> Perhaps I'm missing this, but I read that as the child gets a reference
> to the parent's memory. If the child attempts a write, then new memory
> is allocated, data copied and the write occurs to this new memory. As
> I read this, it's only invoked on a child write.
>
> Would this not leave a hole where the parent could write and, since the
> child shares that memory, the new data would be read by the child? Sort
> of a hidden shm segment? If so, I think we've got problems brewing.
> Now, if a parent write causes the same behaviour as a child write, then
> my point is moot.
Daniel and I discussed this issue when Daniel first came up with
the idea of doing page table COW. He seemed a bit confused by
fork semantics when we first discussed this idea, too ;)
You're right though, both parent and child need to react in the
same way, preferably _without_ having to walk all of the parent's
page tables and mark them read-only ...
kind regards,
Rik
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This archive was generated by hypermail 2b29 : Thu Jan 31 2002 - 21:00:54 EST