Re: [PATCH 6/8] perf,tracing: Prepare the perf-trace interface for RCU changes

[Mathieu Desnoyers]

----- On Feb 12, 2020, at 9:26 AM, rostedt rostedt@xxxxxxxxxxx wrote:

> On Wed, 12 Feb 2020 10:32:16 +0100
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
>> The tracepoint interface will stop providing regular RCU context; make
>> sure we do it ourselves, since perf makes use of regular RCU protected
>> data.
>> 
> 
> Suggested-by: Steven Rostedt (VMware) <rosted@xxxxxxxxxxx>

and

Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>

Thanks :)

Mathieu

> 
>  ;-)
> 
> -- Steve
> 
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
>> ---
>>  kernel/events/core.c |    5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -8950,6 +8950,7 @@ void perf_tp_event(u16 event_type, u64 c
>>  {
>>  	struct perf_sample_data data;
>>  	struct perf_event *event;
>> +	unsigned long rcu_flags;
>>  
>>  	struct perf_raw_record raw = {
>>  		.frag = {
>> @@ -8961,6 +8962,8 @@ void perf_tp_event(u16 event_type, u64 c
>>  	perf_sample_data_init(&data, 0, 0);
>>  	data.raw = &raw;
>>  
>> +	rcu_flags = trace_rcu_enter();
>> +
>>  	perf_trace_buf_update(record, event_type);
>>  
>>  	hlist_for_each_entry_rcu(event, head, hlist_entry) {
>> @@ -8996,6 +8999,8 @@ void perf_tp_event(u16 event_type, u64 c
>>  	}
>>  
>>  	perf_swevent_put_recursion_context(rctx);
>> +
>> +	trace_rcu_exit(rcu_flags);
>>  }
>>  EXPORT_SYMBOL_GPL(perf_tp_event);
>>  

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com