linux-kernel - [Patch v2 1/6] perf/x86/intel: Use early_initcall() to hook bts

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Message-Id: <20250811090034.51249-2-dapeng1.mi@linux.intel.com>
Date: Mon, 11 Aug 2025 17:00:29 +0800
From: Dapeng Mi <dapeng1.mi@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Eranian Stephane <eranian@...gle.com>
Cc: linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	Dapeng Mi <dapeng1.mi@...el.com>,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [Patch v2 1/6] perf/x86/intel: Use early_initcall() to hook bts_init()

After the commit 'd971342d38bf ("perf/x86/intel: Decouple BTS
 initialization from PEBS initialization")' is introduced, x86_pmu.bts
would initialized in bts_init() which is hooked by arch_initcall().

Whereas init_hw_perf_events() is hooked by early_initcall(). Once the
core PMU is initialized, nmi watchdog initialization is called
immediately before bts_init() is called. It leads to the BTS buffer is
not really initialized since bts_init() is not called and x86_pmu.bts is
still false at that time. Worse, BTS buffer would never be initialized
then unless all core PMU events are freed and reserve_ds_buffers()
is called again.

Thus aligning with init_hw_perf_events(), use early_initcall() to hook
bts_init() to ensure x86_pmu.bts is initialized before nmi watchdog
initialization.

Fixes: d971342d38bf ("perf/x86/intel: Decouple BTS initialization from PEBS initialization")
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
---
 arch/x86/events/intel/bts.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 61da6b8a3d51..cbac54cb3a9e 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -643,4 +643,4 @@ static __init int bts_init(void)

 	return perf_pmu_register(&bts_pmu, "intel_bts", -1);
 }
-arch_initcall(bts_init);
+early_initcall(bts_init);
-- 
2.34.1