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    Subject[PATCH 3.12 090/116] powerpc: Fix __get_user_pages_fast() irq handling
    Date
    3.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Heiko Carstens <heiko.carstens@de.ibm.com>

    commit 95f715b08fa4a953771398d20cbe35a6803ea41d upstream.

    __get_user_pages_fast() may be called with interrupts disabled (see e.g.
    get_futex_key() in kernel/futex.c) and therefore should use local_irq_save()
    and local_irq_restore() instead of local_irq_disable()/enable().

    Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/powerpc/mm/gup.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- a/arch/powerpc/mm/gup.c
    +++ b/arch/powerpc/mm/gup.c
    @@ -123,6 +123,7 @@ int __get_user_pages_fast(unsigned long
    struct mm_struct *mm = current->mm;
    unsigned long addr, len, end;
    unsigned long next;
    + unsigned long flags;
    pgd_t *pgdp;
    int nr = 0;

    @@ -156,7 +157,7 @@ int __get_user_pages_fast(unsigned long
    * So long as we atomically load page table pointers versus teardown,
    * we can follow the address down to the the page and take a ref on it.
    */
    - local_irq_disable();
    + local_irq_save(flags);

    pgdp = pgd_offset(mm, addr);
    do {
    @@ -179,7 +180,7 @@ int __get_user_pages_fast(unsigned long
    break;
    } while (pgdp++, addr = next, addr != end);

    - local_irq_enable();
    + local_irq_restore(flags);

    return nr;
    }



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