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Subject[PATCH 5.2 48/61] coresight: tmc-etr: alloc_perf_buf: Do not call smp_processor_id from preemptible
Date
From: Suzuki K Poulose <suzuki.poulose@arm.com>

commit 3a8710392db2c70f74aed6f06b16e8bec0f05a35 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/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

Use NUMA_NO_NODE hint instead of using the current node for events
not bound to CPUs.

Fixes: 22f429f19c4135d51e9 ("coresight: etm-perf: Add support for ETR backend")
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: stable <stable@vger.kernel.org> # 4.20+
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20190620221237.3536-3-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/hwtracing/coresight/coresight-tmc-etr.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1178,14 +1178,11 @@ 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_NO_NODE : cpu_to_node(event->cpu);
/*
* Try to match the perf ring buffer size if it is larger
* than the size requested via sysfs.

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