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

Steven Rostedt
2020-02-12T14:26:59Z

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>

;-)

-- 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);
>
>