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SubjectRe: process 'stuck' at exit.
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On Tue, Dec 10, 2013 at 1:41 PM, Dave Jones <davej@redhat.com> wrote:
>
> http://codemonkey.org.uk/junk/trace

Hmm. Ok, so something is calling [__]get_user_pages_fast() and
put_page() in a loop, but the trace doesn't show what that "something"
is, because it is itself not ever called.

However, that pattern does seem to imply that the loop is in
get_futex_key(), because all the other loops I see seem to be calling
other things as well.

And the __get_user_pages_fast() call implies that it's the THP case
that triggers the "unlikely(PageTail(page))" case. And anyway,
otherwise we'd see lock_page()/unlock_page() too.

So it looks like __get_user_pages_fast() fails, and keeps failing.
Andrea, this is your code, any ideas? Commit a5b338f2b0b1f ("thp:
update futex compound knowledge") to be exact.

Linus


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