linux-kernel - [PATCH v4 3/4] perf/core: Remove pmu linear searching code

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Date:   Thu, 4 May 2023 16:30:02 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     <peterz@...radead.org>
CC:     <ravi.bangoria@....com>, <namhyung@...nel.org>,
        <eranian@...gle.com>, <acme@...nel.org>, <mark.rutland@....com>,
        <jolsa@...nel.org>, <irogers@...gle.com>, <bp@...en8.de>,
        <kan.liang@...ux.intel.com>, <adrian.hunter@...el.com>,
        <maddy@...ux.ibm.com>, <x86@...nel.org>,
        <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <sandipan.das@....com>, <ananth.narayan@....com>,
        <santosh.shukla@....com>
Subject: [PATCH v4 3/4] perf/core: Remove pmu linear searching code

Searching for the right pmu by iterating over all pmus is no longer
required since all pmus now *must* be present in the 'pmu_idr' list.
So, remove linear searching code.

Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
---
 kernel/events/core.c | 37 +++++++++++++------------------------
 1 file changed, 13 insertions(+), 24 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0695bb9fbbb6..eba2b8595115 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11630,38 +11630,27 @@ static struct pmu *perf_init_event(struct perf_event *event)
 	}
 
 again:
+	ret = -ENOENT;
 	rcu_read_lock();
 	pmu = idr_find(&pmu_idr, type);
 	rcu_read_unlock();
-	if (pmu) {
-		if (event->attr.type != type && type != PERF_TYPE_RAW &&
-		    !(pmu->capabilities & PERF_PMU_CAP_EXTENDED_HW_TYPE))
-			goto fail;
-
-		ret = perf_try_init_event(pmu, event);
-		if (ret == -ENOENT && event->attr.type != type && !extended_type) {
-			type = event->attr.type;
-			goto again;
-		}
+	if (!pmu)
+		goto fail;
 
-		if (ret)
-			pmu = ERR_PTR(ret);
+	if (event->attr.type != type && type != PERF_TYPE_RAW &&
+	    !(pmu->capabilities & PERF_PMU_CAP_EXTENDED_HW_TYPE))
+		goto fail;
 
-		goto unlock;
+	ret = perf_try_init_event(pmu, event);
+	if (ret == -ENOENT && event->attr.type != type && !extended_type) {
+		type = event->attr.type;
+		goto again;
 	}
 
-	list_for_each_entry_rcu(pmu, &pmus, entry, lockdep_is_held(&pmus_srcu)) {
-		ret = perf_try_init_event(pmu, event);
-		if (!ret)
-			goto unlock;
-
-		if (ret != -ENOENT) {
-			pmu = ERR_PTR(ret);
-			goto unlock;
-		}
-	}
 fail:
-	pmu = ERR_PTR(-ENOENT);
+	if (ret)
+		pmu = ERR_PTR(ret);
+
 unlock:
 	srcu_read_unlock(&pmus_srcu, idx);
 
-- 
2.40.0