linux-kernel - [tip: perf/core] perf/x86/intel: Use early_initcall() to hook bts

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Message-ID: <175611746972.1420.7955373348082581195.tip-bot2@tip-bot2>
Date: Mon, 25 Aug 2025 10:24:29 -0000
From: "tip-bot2 for Dapeng Mi" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Dapeng Mi <dapeng1.mi@...ux.intel.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Kan Liang <kan.liang@...ux.intel.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: perf/core] perf/x86/intel: Use early_initcall() to hook bts_init()

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     d9cf9c6884d21e01483c4e17479d27636ea4bb50
Gitweb:        https://git.kernel.org/tip/d9cf9c6884d21e01483c4e17479d27636ea4bb50
Author:        Dapeng Mi <dapeng1.mi@...ux.intel.com>
AuthorDate:    Wed, 20 Aug 2025 10:30:26 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 21 Aug 2025 20:09:26 +02:00

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
Link: https://lore.kernel.org/r/20250820023032.17128-2-dapeng1.mi@linux.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 61da6b8..cbac54c 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);