This is a note to let you know that I've just added the patch titled coresight: tmc-etf: Do not call smp_processor_id from preemptible to the 4.19-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-tmc-etf-do-not-call-smp_processor_id-from-preemptible.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 024c1fd9dbcc1d8a847f1311f999d35783921b7f Mon Sep 17 00:00:00 2001 From: Suzuki K Poulose <suzuki.poulose@xxxxxxx> Date: Thu, 20 Jun 2019 16:12:35 -0600 Subject: coresight: tmc-etf: Do not call smp_processor_id from preemptible From: Suzuki K Poulose <suzuki.poulose@xxxxxxx> 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@xxxxxxxxxx> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.7+ Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> Link: https://lore.kernel.org/r/20190620221237.3536-4-mathieu.poirier@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -304,9 +304,7 @@ 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); Patches currently in stable-queue which might be from suzuki.poulose@xxxxxxx are queue-4.19/coresight-tmc-etf-do-not-call-smp_processor_id-from-preemptible.patch queue-4.19/coresight-etb10-do-not-call-smp_processor_id-from-preemptible.patch