linux-kernel - [PATCH -fixes] drivers: perf: Fix smp_processor

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Message-Id: <20240826165210.124696-1-alexghiti@rivosinc.com>
Date: Mon, 26 Aug 2024 18:52:10 +0200
From: Alexandre Ghiti <alexghiti@...osinc.com>
To: Atish Patra <atishp@...shpatra.org>,
	Anup Patel <anup@...infault.org>,
	Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	linux-riscv@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Alexandre Ghiti <alexghiti@...osinc.com>,
	Nam Cao <namcao@...utronix.de>
Subject: [PATCH -fixes] drivers: perf: Fix smp_processor_id() use in preemptible code

As reported in [1], the use of smp_processor_id() in
pmu_sbi_device_probe() must be protected by disabling the preemption, so
simple use get_cpu()/put_cpu() instead.

Reported-by: Nam Cao <namcao@...utronix.de>
Closes: https://lore.kernel.org/linux-riscv/20240820074925.ReMKUPP3@linutronix.de/ [1]
Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
 drivers/perf/riscv_pmu_sbi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 31a17a56eb3b..25b1b699b3e2 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -1373,11 +1373,15 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 
 	/* SBI PMU Snapsphot is only available in SBI v2.0 */
 	if (sbi_v2_available) {
+		int cpu;
+
 		ret = pmu_sbi_snapshot_alloc(pmu);
 		if (ret)
 			goto out_unregister;
 
-		ret = pmu_sbi_snapshot_setup(pmu, smp_processor_id());
+		cpu = get_cpu();
+
+		ret = pmu_sbi_snapshot_setup(pmu, cpu);
 		if (ret) {
 			/* Snapshot is an optional feature. Continue if not available */
 			pmu_sbi_snapshot_free(pmu);
@@ -1391,6 +1395,7 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 			 */
 			static_branch_enable(&sbi_pmu_snapshot_available);
 		}
+		put_cpu();
 	}
 
 	register_sysctl("kernel", sbi_pmu_sysctl_table);
-- 
2.39.2