linux-kernel - [PATCH -fixes] drivers: perf: Fix wrong put

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Message-Id: <20241112113422.617954-1-alexghiti@rivosinc.com>
Date: Tue, 12 Nov 2024 12:34:22 +0100
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>,
	Atish Patra <atishp@...osinc.com>
Subject: [PATCH -fixes] drivers: perf: Fix wrong put_cpu() placement

Unfortunately, the wrong patch version was merged which places the
put_cpu() after enabling a static key, which is not safe as pointed by
Will [1], so move put_cpu() before to avoid this.

Fixes: 2840dadf0dde ("drivers: perf: Fix smp_processor_id() use in preemptible code")
Reported-by: Atish Patra <atishp@...osinc.com>
Link: https://lore.kernel.org/all/20240827125335.GD4772@willie-the-truck/ [1]
Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
 drivers/perf/riscv_pmu_sbi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 391ca1422cae..1aa303f76cc7 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -1393,8 +1393,9 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 			goto out_unregister;
 
 		cpu = get_cpu();
-
 		ret = pmu_sbi_snapshot_setup(pmu, cpu);
+		put_cpu();
+
 		if (ret) {
 			/* Snapshot is an optional feature. Continue if not available */
 			pmu_sbi_snapshot_free(pmu);
@@ -1408,7 +1409,6 @@ 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