Re: MIPS: Make set_pte() SMP safe.

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On 08/04/2015 12:15 PM, Leonid Yegoshin wrote:
David,

Did you observe this in real?

Yes.  It is not hypothetical.


The function __get_vm_area_node() allocates a guard page if flag
VM_NO_GUARD is not used and I don't see any use of it in source.

In past vmap allocated a guard page even unconditionally.

It has nothing to do with guard pages per se. The problem is if a vmap range (including guard page) ends on an even PFN. The buddy code will clobber the PTE for PFN+1. If another vmap operation is executing in set_pte() for the clobbered location, you can get corrupted page tables.



- Leonid.






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