Hi Mathieu,
On 07/18/2018 08:43 PM, Mathieu Poirier wrote:
When enabling the lockdep mechanic and working with CPU-wide scenarios we
get the following console output:
This is fixed by working with the cpu_present_mask, avoinding at the same
the need to use get/put_online_cpus() that triggers lockdep.
The patch looks correct to me. In fact I have a patch [1], which
does the same thing and switches to using per-cpu variable for the
paths.
Signed-off-by: Mathieu Poirier <[email protected]>
---
drivers/hwtracing/coresight/coresight-etm-perf.c | 39 +++++++++++++-----------
1 file changed, 21 insertions(+), 18 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c
b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 677695635211..16b9c87d9d00 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -108,26 +108,32 @@ static int etm_event_init(struct perf_event *event)
static void free_event_data(struct work_struct *work)
{
int cpu;
+ void *snk_config;
cpumask_t *mask;
struct etm_event_data *event_data;
struct coresight_device *sink;
event_data = container_of(work, struct etm_event_data, work);
mask = &event_data->mask;
- /*
- * First deal with the sink configuration. See comment in
- * etm_setup_aux() about why we take the first available path.
- */
- if (event_data->snk_config) {
- cpu = cpumask_first(mask);
- sink = coresight_get_sink(event_data->path[cpu]);
- if (sink_ops(sink)->free_buffer)
- sink_ops(sink)->free_buffer(event_data->snk_config);
- }
+ snk_config = event_data->snk_config;
for_each_cpu(cpu, mask) {
- if (!(IS_ERR_OR_NULL(event_data->path[cpu])))
- coresight_release_path(event_data->path[cpu]);
+ if (IS_ERR_OR_NULL(event_data->path[cpu]))
+ continue;
+
+ /*
+ * Free sink configuration - there can only be one sink
+ * per event.
+ */
+ if (snk_config) {
+ sink = coresight_get_sink(event_data->path[cpu]);
+ if (sink_ops(sink)->free_buffer) {
+ sink_ops(sink)->free_buffer(snk_config);
+ snk_config = NULL;
+ }
+ }
+
+ coresight_release_path(event_data->path[cpu]);
}
kfree(event_data->path);
@@ -145,16 +151,13 @@ static void *alloc_event_data(int cpu)
if (!event_data)
return NULL;
- /* Make sure nothing disappears under us */
- get_online_cpus();
- size = num_online_cpus();
-
mask = &event_data->mask;
+ size = num_present_cpus();
+
if (cpu != -1)
cpumask_set_cpu(cpu, mask);
else
- cpumask_copy(mask, cpu_online_mask);
- put_online_cpus();
+ cpumask_copy(mask, cpu_present_mask);
I think it is safe to use cpu_online_mask outside the
get/put_online_cpus(). Using present_mask may fail as
we could fail to create a path for a CPU that is not online.
Please could you check if [1] fixes the problem for you ?
[1]
http://lists.infradead.org/pipermail/linux-arm-kernel/2018-July/591606.html
Cheers
Suzuki
