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    Subject[PATCH 4.9 264/271] coresight: tmc-etf: Do not call smp_processor_id from preemptible
    Date
    From: Suzuki K Poulose <suzuki.poulose@arm.com>

    commit 024c1fd9dbcc1d8a847f1311f999d35783921b7f upstream.

    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
    caller is tmc_alloc_etf_buffer+0x5c/0x60
    CPU: 2 PID: 2544 Comm: perf Not tainted 5.1.0-rc6-147786-g116841e #344
    Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Feb 1 2019
    Call trace:
    dump_backtrace+0x0/0x150
    show_stack+0x14/0x20
    dump_stack+0x9c/0xc4
    debug_smp_processor_id+0x10c/0x110
    tmc_alloc_etf_buffer+0x5c/0x60
    etm_setup_aux+0x1c4/0x230
    rb_alloc_aux+0x1b8/0x2b8
    perf_mmap+0x35c/0x478
    mmap_region+0x34c/0x4f0
    do_mmap+0x2d8/0x418
    vm_mmap_pgoff+0xd0/0xf8
    ksys_mmap_pgoff+0x88/0xf8
    __arm64_sys_mmap+0x28/0x38
    el0_svc_handler+0xd8/0x138
    el0_svc+0x8/0xc

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

    Fixes: 2e499bbc1a929ac ("coresight: tmc: implementing TMC-ETF AUX space API")
    Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    Cc: stable <stable@vger.kernel.org> # 4.7+
    Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    Link: https://lore.kernel.org/r/20190620221237.3536-4-mathieu.poirier@linaro.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/hwtracing/coresight/coresight-tmc-etf.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
    +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
    @@ -292,9 +292,7 @@ static void *tmc_alloc_etf_buffer(struct
    int node;
    struct cs_buffers *buf;

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

    /* Allocate memory structure for interaction with Perf */
    buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node);

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