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    Subject[PATCH 4.14 66/74] coresight: etb10: Do not call smp_processor_id from preemptible
    Date
    From: Suzuki K Poulose <suzuki.poulose@arm.com>

    [ Upstream commit 730766bae3280a25d40ea76a53dc6342e84e6513 ]

    During a perf session we try to allocate buffers on the "node" associated
    with the CPU the event is bound to. If it is not bound to a CPU, we
    use the current CPU node, using smp_processor_id(). However this is unsafe
    in a pre-emptible context and could generate the splats as below :

    BUG: using smp_processor_id() in preemptible [00000000] code: perf/2544

    Use NUMA_NO_NODE hint instead of using the current node for events
    not bound to CPUs.

    Fixes: 2997aa4063d97fdb39 ("coresight: etb10: implementing AUX API")
    Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    Cc: stable <stable@vger.kernel.org> # 4.6+
    Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    Link: https://lore.kernel.org/r/20190620221237.3536-5-mathieu.poirier@linaro.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/hwtracing/coresight/coresight-etb10.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
    index d14a9cb7959a..7fcf70b2163d 100644
    --- a/drivers/hwtracing/coresight/coresight-etb10.c
    +++ b/drivers/hwtracing/coresight/coresight-etb10.c
    @@ -287,9 +287,7 @@ static void *etb_alloc_buffer(struct coresight_device *csdev, int cpu,
    int node;
    struct cs_buffers *buf;

    - if (cpu == -1)
    - cpu = smp_processor_id();
    - node = cpu_to_node(cpu);
    + node = (event->cpu == -1) ? NUMA_NO_NODE : cpu_to_node(event->cpu);

    buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node);
    if (!buf)
    --
    2.20.1


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