• Will Deacon's avatar
    arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables · 20a004e7
    Will Deacon authored
    In many cases, page tables can be accessed concurrently by either another
    CPU (due to things like fast gup) or by the hardware page table walker
    itself, which may set access/dirty bits. In such cases, it is important
    to use READ_ONCE/WRITE_ONCE when accessing page table entries so that
    entries cannot be torn, merged or subject to apparent loss of coherence
    due to compiler transformations.
    
    Whilst there are some scenarios where this cannot happen (e.g. pinned
    kernel mappings for the linear region), the overhead of using READ_ONCE
    /WRITE_ONCE everywhere is minimal and makes the code an awful lot easier
    to reason about. This patch consistently uses these macros in the arch
    code, as well as explicitly namespacing pointers to page table entries
    from the entries themselves by using adopting a 'p' suffix for the former
    (as is sometimes used elsewhere in the kernel source).
    Tested-by: default avatarYury Norov <ynorov@caviumnetworks.com>
    Tested-by: default avatarRichard Ruigrok <rruigrok@codeaurora.org>
    Reviewed-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    20a004e7
hugetlb.h 2.72 KB