We find the current CPU using smp_processor_id() if the event is not bound
to a CPU, to find the node for memory allocation. Use the safe
numa_node_id() instead, to avoid BUG(). e.g:

 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

Fixes: 2e499bbc1a929ac ("coresight: tmc: implementing TMC-ETF AUX space API")
Cc: Mathieu Poirier <mathieu.poir...@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com>
---
 drivers/hwtracing/coresight/coresight-tmc-etf.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c 
b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index 31093de..5d0e594 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -377,12 +377,10 @@ static void *tmc_alloc_etf_buffer(struct coresight_device 
*csdev,
                                  struct perf_event *event, void **pages,
                                  int nr_pages, bool overwrite)
 {
-       int node, cpu = event->cpu;
+       int node;
        struct cs_buffers *buf;
 
-       if (cpu == -1)
-               cpu = smp_processor_id();
-       node = cpu_to_node(cpu);
+       node = (event->cpu == -1) ? numa_node_id() : cpu_to_node(event->cpu);
 
        /* Allocate memory structure for interaction with Perf */
        buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node);
-- 
2.7.4

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