On Sat, 10 Feb 2007, Eric Dumazet wrote:
>
> Well, I guess if the original program was mono-threaded, and syscall used
> fget_light(), we might have a problem here if the child try a close(). So you
> may have to disable fget_light() magic if async call is the originator of the
> syscall.
Yes. All the issues that I already brought up with Zach's patches are
still there. This doesn't really change any of them. Any optimization that
checks for "am I single-threaded" will need to be aware of pending and
running async things.
With my patch, any _running_ async things will always be seen as normal
clones, but the pending ones won't. So you'd need to effectively change
anything that looks like
if (atomic_read(¤t->mm->count) == 1)
.. do some simplified version ..
into
if (!current->async_cookie && atomic_read(..) == 1)
.. do the simplified thing ..
to make it safe.
I think we only do it for fget_light and some VM TLB simplification, so it
shouldn't be a big burden to check.
Side note: the real issues still remain. The interfaces, and the
performance testing.
Linus
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