The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 730766bae3280a25d40ea76a53dc6342e84e6513 Mon Sep 17 00:00:00 2001

From: Suzuki K Poulose suzuki.poulose@arm.com Date: Thu, 20 Jun 2019 16:12:36 -0600 Subject: [PATCH] coresight: etb10: Do not call smp_processor_id from preemptible

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

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index d5b9edecf76e..3810290e6d07 100644 --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -374,12 +374,10 @@ static void *etb_alloc_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_NO_NODE : cpu_to_node(event->cpu);

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