linux-kernel - [PATCH] perf/core: move all of the pmu devices into their own location

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Message-ID: <2025020304-chip-trench-4e56@gregkh>
Date: Mon,  3 Feb 2025 20:25:05 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>
Subject: [PATCH] perf/core: move all of the pmu devices into their own location

In sysfs, for some reason, all pmu devices seem to show up in the "root"
of /sys/devices/ making for a confusing mess as these devices are not
really at the root of the system at all.

Create a fake root devices, "pmu_bus" and place them all under there if
they do not already have a parent device set, cleaning up sysfs to look
more sane.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Ian Rogers <irogers@...gle.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: "Liang, Kan" <kan.liang@...ux.intel.com>
Cc: linux-perf-users@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---

Note, if you all don't like "pmu_bus" for the name, that's fine, please
let me know and I can rename it to something else, but it should be
something to get these objects out of the root sysfs directory.

 kernel/events/core.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index bcb09e011e9e..786537faed2c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11767,6 +11767,11 @@ static const struct attribute_group *pmu_dev_groups[] = {
 };
 
 static int pmu_bus_running;
+
+static struct device pmu_bus_root = {
+	.init_name	= "pmu_bus",
+};
+
 static struct bus_type pmu_bus = {
 	.name		= "event_source",
 	.dev_groups	= pmu_dev_groups,
@@ -11790,7 +11795,10 @@ static int pmu_dev_alloc(struct pmu *pmu)
 
 	dev_set_drvdata(pmu->dev, pmu);
 	pmu->dev->bus = &pmu_bus;
-	pmu->dev->parent = pmu->parent;
+	if (pmu->parent)
+		pmu->dev->parent = pmu->parent;
+	else
+		pmu->dev->parent = &pmu_bus_root;
 	pmu->dev->release = pmu_dev_release;
 
 	ret = dev_set_name(pmu->dev, "%s", pmu->name);
@@ -14232,9 +14240,17 @@ static int __init perf_event_sysfs_init(void)
 
 	mutex_lock(&pmus_lock);
 
-	ret = bus_register(&pmu_bus);
-	if (ret)
+	ret = device_register(&pmu_bus_root);
+	if (ret) {
+		put_device(&pmu_bus_root);
 		goto unlock;
+	}
+
+	ret = bus_register(&pmu_bus);
+	if (ret) {
+		device_unregister(&pmu_bus_root);
+		goto unlock;
+	}
 
 	list_for_each_entry(pmu, &pmus, entry) {
 		if (pmu->dev)
-- 
2.48.1