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    SubjectRe: [PATCH] ARM: cache-v7: Disable preemption when reading CCSIDR
    On Fri, Feb 03, 2012 at 02:03:49AM +0000, Stephen Boyd wrote:
    > armv7's flush_cache_all() flushes caches via set/way. To
    > determine the cache attributes (line size, number of sets,
    > etc.) the assembly first writes the CSSELR register to select a
    > cache level and then reads the CCSIDR register. The CSSELR register
    > is banked per-cpu and is used to determine which cache level CCSIDR
    > reads. If the task is migrated between when the CSSELR is written and
    > the CCSIDR is read the CCSIDR value may be for an unexpected cache
    > level (for example L1 instead of L2) and incorrect cache flushing
    > could occur.
    >
    > Disable interrupts across the write and read so that the correct
    > cache attributes are read and used for the cache flushing
    > routine. We disable interrupts instead of disabling preemption
    > because the critical section is only 3 instructions and we want
    > to call v7_dcache_flush_all from __v7_setup which doesn't have a
    > full kernel stack with a struct thread_info.
    >
    > This fixes a problem we see in scm_call() when flush_cache_all()
    > is called from preemptible context and sometimes the L2 cache is
    > not properly flushed out.
    >
    > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
    > Cc: Catalin Marinas <catalin.marinas@arm.com>
    > Cc: Nicolas Pitre <nico@fluxnic.net>

    Acked-by: Catalin Marinas <catalin.marinas@arm.com>

    --
    Catalin


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