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

Mathieu Desnoyers
2020-02-12T15:07:56Z

----- On Feb 12, 2020, at 9:26 AM, rostedt rostedt@goodmis.org wrote:

> On Wed, 12 Feb 2020 10:32:16 +0100
> Peter Zijlstra <peterz@infradead.org> 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@goodmis.org>

and

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

Thanks :)

Mathieu

>
> ;-)
>
> -- Steve
>
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>> ---
>> 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.