| Subject | Re: [PATCH 4.19 103/115] coresight: etb10: Do not call smp_processor_id from preemptible | From | Suzuki Kuruppassery Poulose <> | Date | Wed, 8 Jan 2020 11:01:41 +0000 |
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Greg,
On 07/01/2020 20:55, Greg Kroah-Hartman wrote: > From: Suzuki K Poulose <suzuki.poulose@arm.com> > > [ Upstream commit 730766bae3280a25d40ea76a53dc6342e84e6513 ] > > 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> > Signed-off-by: Sasha Levin <sashal@kernel.org> > --- > drivers/hwtracing/coresight/coresight-etb10.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c > index 0dad8626bcfb..0a59bf3af40b 100644 > --- a/drivers/hwtracing/coresight/coresight-etb10.c > +++ b/drivers/hwtracing/coresight/coresight-etb10.c > @@ -275,9 +275,7 @@ static void *etb_alloc_buffer(struct coresight_device *csdev, int 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);
Please drop this patch too, from the list as it will break the build with undefined "event" variable. I will post a backport soon.
Suzuki
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