linux-kernel - [PATCH v4 18/22] perf: Add a helper for looking up pmus by type

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Date:	Wed, 20 Aug 2014 15:36:15 +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,
	Robert Richter <rric@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v4 18/22] 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 b82392911a..550c22a2b7 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6930,6 +6930,18 @@ void perf_pmu_unregister(struct pmu *pmu)
 }
 EXPORT_SYMBOL_GPL(perf_pmu_unregister);
 
+/* 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;
+}
+
 struct pmu *perf_init_event(struct perf_event *event)
 {
 	struct pmu *pmu = NULL;
@@ -6938,9 +6950,7 @@ 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) {
 		if (!try_module_get(pmu->module)) {
 			pmu = ERR_PTR(-ENODEV);
-- 
2.1.0

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