On Fri, Dec 21, 2012 at 10:21 AM, Hugh Dickins [off-list ref] wrote:

On Fri, 21 Dec 2012, Linus Torvalds wrote:

quoted

compared to the diseased abortion you just posted.

I'm picking up a vibe that you don't entirely like Mel's approach.

Good job. I was a bit nervous that I was being too subtle.

I don't understand David's and Mel's remarks about the "shared pages"
check making Sasha's warning unlikely: page_mapcount has nothing to do
with whether a page belongs to shm/shmem/tmpfs, and it's easy enough
to reproduce Sasha's warning on the current git tree.  "mount -o
remount,mpol=local /tmp" or something like that is useful in testing.

I think that Mel and David may talk about the mutex actually blocking
(not just the debug message possibly triggering).

I wish wish wish I had time to spend on this today, but I don't.
And I've not looked to see (let alone tested) whether it's easy
to revert Mel's mutex then add in Kosaki's patch (which I didn't
look at so have no opinion on).

I don't actually have Kosaki's patch either, just the description of
it. We've done that kind of "preallocate before taking the lock"
before, though.

Shall we go for Peter/David's mutex+spinlock for rc1 - I assume
they both tested that - with a promise to do better in rc2?

Well, if the plan is to fix it for rc2, then there is no point in
putting a workaround in now, since actually hitting the problem (as
opposed to seeing the warning) is presumably much harder.

               Linus

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