linux-kernel - [PATCH v4 14/27] perf,tracing: Prepare the perf-trace interface for RCU changes

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Date:   Fri, 21 Feb 2020 14:34:30 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        rostedt@...dmis.org
Cc:     peterz@...radead.org, mingo@...nel.org, joel@...lfernandes.org,
        gregkh@...uxfoundation.org, gustavo@...eddedor.com,
        tglx@...utronix.de, paulmck@...nel.org, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        luto@...nel.org, tony.luck@...el.com, frederic@...nel.org,
        dan.carpenter@...cle.com, mhiramat@...nel.org,
        "Steven Rostedt (VMware)" <rosted@...dmis.org>
Subject: [PATCH v4 14/27] perf,tracing: Prepare the perf-trace interface for RCU changes

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@...dmis.org>
Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.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;
+	int 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);