[PATCH -fixes] drivers: perf: Fix smp_processor_id() use in preemptible code

From: Alexandre Ghiti
Date: Mon Aug 26 2024 - 12:52:22 EST


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@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-riscv/20240820074925.ReMKUPP3@xxxxxxxxxxxxx/ [1]
Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
---
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