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    SubjectRe: Should mmap MAP_LOCKED fail if mm_poppulate fails?
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    On Tue, Apr 28, 2015 at 9:43 AM, Michal Hocko <mhocko@suse.cz> wrote:
    >
    > Hmm, no other thread has the address from the current mmap call except
    > for MAP_FIXED (more on that below).

    With things like opportunistic SIGSEGV handlers that map/unmap things
    as the user takes faults, that's actually not at all guaranteed.

    Yeah, it's unusual, but I've seen it, with threaded applications where
    people play games with user-space memory management, and do "demand
    allocation" with mmap() in response to signals.

    Admittedly we already do bad things in mmap(MAP_FIXED) for that case,
    since we dropped the vm lock. But at least it shouldn't be any worse
    than a thread speculatively touching the pages..

    Linus


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