• David S. Miller's avatar
    sparc64: Fix tsb_grow() in atomic context. · 0fbebed6
    David S. Miller authored
    If our first THP installation for an MM is via the set_pmd_at() done
    during khugepaged's collapsing we'll end up in tsb_grow() trying to do
    a GFP_KERNEL allocation with several locks held.
    
    Simply using GFP_ATOMIC in this situation is not the best option
    because we really can't have this fail, so we'd really like to keep
    this an order 0 GFP_KERNEL allocation if possible.
    
    Also, doing the TSB allocation from khugepaged is a really bad idea
    because we'll allocate it potentially from the wrong NUMA node in that
    context.
    
    So what we do is defer the hugepage TSB allocation until the first TLB
    miss we take on a hugepage.  This is slightly tricky because we have
    to handle two unusual cases:
    
    1) Taking the first hugepage TLB miss in the window trap handler.
       We'll call the winfix_trampoline when that is detected.
    
    2) An initial TSB allocation via TLB miss races with a hugetlb
       fault on another cpu running the same MM.  We handle this by
       unconditionally loading the TSB we see into the current cpu
       even if it's non-NULL at hugetlb_setup time.
    Reported-by: default avatarMeelis Roos <mroos@ut.ee>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    0fbebed6
tsb.S 13 KB