This is a note to let you know that I've just added the patch titled coresight: etb10: Do not call smp_processor_id from preemptible to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: coresight-etb10-do-not-call-smp_processor_id-from-preemptible.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 730766bae3280a25d40ea76a53dc6342e84e6513 Mon Sep 17 00:00:00 2001 From: Suzuki K Poulose <suzuki.poulose@xxxxxxx> Date: Thu, 20 Jun 2019 16:12:36 -0600 Subject: coresight: etb10: Do not call smp_processor_id from preemptible From: Suzuki K Poulose <suzuki.poulose@xxxxxxx> commit 730766bae3280a25d40ea76a53dc6342e84e6513 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 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@xxxxxxxxxx> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.6+ Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> Link: https://lore.kernel.org/r/20190620221237.3536-5-mathieu.poirier@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/hwtracing/coresight/coresight-etb10.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -279,9 +279,7 @@ static void *etb_alloc_buffer(struct cor 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); buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node); if (!buf) Patches currently in stable-queue which might be from suzuki.poulose@xxxxxxx are queue-4.9/coresight-tmc-etf-do-not-call-smp_processor_id-from-preemptible.patch queue-4.9/coresight-etb10-do-not-call-smp_processor_id-from-preemptible.patch