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    SubjectRe: bio linked list corruption.
    On Thu, Oct 20, 2016 at 4:03 PM, Dave Jones <davej@codemonkey.org.uk> wrote:
    > On Thu, Oct 20, 2016 at 04:01:12PM -0700, Andy Lutomirski wrote:
    > > On Thu, Oct 20, 2016 at 3:50 PM, Dave Jones <davej@codemonkey.org.uk> wrote:
    > > > On Tue, Oct 18, 2016 at 06:05:57PM -0700, Andy Lutomirski wrote:
    > > >
    > > > > One possible debugging approach would be to change:
    > > > >
    > > > > #define NR_CACHED_STACKS 2
    > > > >
    > > > > to
    > > > >
    > > > > #define NR_CACHED_STACKS 0
    > > > >
    > > > > in kernel/fork.c and to set CONFIG_DEBUG_PAGEALLOC=y. The latter will
    > > > > force an immediate TLB flush after vfree.
    > > >
    > > > I can give that idea some runtime, but it sounds like this a case where
    > > > we're trying to prove a negative, and that'll just run and run ? In which case I
    > > > might do this when I'm travelling on Sunday.
    > >
    > > The idea is that the stack will be free and unmapped immediately upon
    > > process exit if configured like this so that bogus stack accesses (by
    > > the CPU, not DMA) would OOPS immediately.
    >
    > oh, misparsed. ok, I can definitely get behind that idea then.
    > I'll do that next.
    >

    It could be worth trying this, too:

    https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/vmap_stack&id=174531fef4e8

    It occurred to me that the current code is a little bit fragile.

    --Andy

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