[PATCH 2/4] coresight: tmc-etr: alloc_perf_buf: Do not call smp_processor_id from preemptible

[Suzuki K Poulose]

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().

 BUG: using smp_processor_id() in preemptible [00000000] code: perf/1743
 caller is tmc_alloc_etr_buffer+0x1bc/0x1f0
 CPU: 1 PID: 1743 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_etr_buffer+0x1bc/0x1f0
  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: 22f429f19c4135d51e9 ("coresight: etm-perf: Add support for ETR backend")
Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index cae9d8a..e2932f5 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1184,14 +1184,11 @@ static struct etr_buf *
 alloc_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 	      int nr_pages, void **pages, bool snapshot)
 {
-	int node, cpu = event->cpu;
+	int node;
 	struct etr_buf *etr_buf;
 	unsigned long size;
 
-	if (cpu == -1)
-		cpu = smp_processor_id();
-	node = cpu_to_node(cpu);
-
+	node = (event->cpu == -1) ? numa_node_id() : cpu_to_node(event->cpu);
 	/*
 	 * Try to match the perf ring buffer size if it is larger
 	 * than the size requested via sysfs.
-- 
2.7.4