The CPU_DYING notifier modifies the per-cpu pointer pmu->box, and this can
race with functions such as uncore_pmu_to_box() and uncore_pci_remove() when
we remove stop_machine() from the CPU offline path. So protect them using
get/put_online_cpus_atomic().
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/perf_event_intel_uncore.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 9dd9975..7c2a064 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -1,3 +1,4 @@
+#include <linux/cpu.h>
#include "perf_event_intel_uncore.h"
static struct intel_uncore_type *empty_uncore[] = { NULL, };
@@ -2630,6 +2631,7 @@ uncore_pmu_to_box(struct intel_uncore_pmu *pmu, int cpu)
if (box)
return box;
+ get_online_cpus_atomic();
raw_spin_lock(&uncore_box_lock);
list_for_each_entry(box, &pmu->box_list, list) {
if (box->phys_id == topology_physical_package_id(cpu)) {
@@ -2639,6 +2641,7 @@ uncore_pmu_to_box(struct intel_uncore_pmu *pmu, int cpu)
}
}
raw_spin_unlock(&uncore_box_lock);
+ put_online_cpus_atomic();
return *per_cpu_ptr(pmu->box, cpu);
}
@@ -3229,6 +3232,7 @@ static void uncore_pci_remove(struct pci_dev *pdev)
list_del(&box->list);
raw_spin_unlock(&uncore_box_lock);
+ get_online_cpus_atomic();
for_each_possible_cpu(cpu) {
if (*per_cpu_ptr(pmu->box, cpu) == box) {
*per_cpu_ptr(pmu->box, cpu) = NULL;
@@ -3237,6 +3241,8 @@ static void uncore_pci_remove(struct pci_dev *pdev)
}
WARN_ON_ONCE(atomic_read(&box->refcnt) != 1);
+ put_online_cpus_atomic();
+
kfree(box);
}
--
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