linux-kernel - [RFC PATCH 3/6] perf: Add a helper for looking up pmus by type

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Date:   Fri, 23 Sep 2016 14:27:23 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        vince@...ter.net, eranian@...gle.com,
        Arnaldo Carvalho de Melo <acme@...radead.org>,
        tglx@...utronix.de, ak@...ux.intel.com,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [RFC PATCH 3/6] perf: Add a helper for looking up pmus by type

This patch adds a helper for looking up a registered pmu by its type.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 kernel/events/core.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2e8a0e389b..b64a5c611f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8780,6 +8780,18 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
 	return ret;
 }
 
+/* call under pmus_srcu */
+static struct pmu *__perf_find_pmu(u32 type)
+{
+	struct pmu *pmu;
+
+	rcu_read_lock();
+	pmu = idr_find(&pmu_idr, type);
+	rcu_read_unlock();
+
+	return pmu;
+}
+
 static struct pmu *perf_init_event(struct perf_event *event)
 {
 	struct pmu *pmu = NULL;
@@ -8788,9 +8800,7 @@ static struct pmu *perf_init_event(struct perf_event *event)
 
 	idx = srcu_read_lock(&pmus_srcu);
 
-	rcu_read_lock();
-	pmu = idr_find(&pmu_idr, event->attr.type);
-	rcu_read_unlock();
+	pmu = __perf_find_pmu(event->attr.type);
 	if (pmu) {
 		ret = perf_try_init_event(pmu, event);
 		if (ret)
-- 
2.9.3