[Xen-devel] [PATCH v4 09/10] xen/arm: Free memory allocated for sibling/core maps on CPU hot-unplug

[Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>]

The memory allocated in setup_cpu_sibling_map() when a CPU is hotplugged
has to be freed when the CPU is hot-unplugged. This is done in
remove_cpu_sibling_map() and called when the CPU dies. The call to
remove_cpu_sibling_map() is made from a notifier callback when
CPU_DEAD event is received.

Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>

---
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
---
Changes in v3:
-Use notifier to trigger remove_cpu_sibling_map() when the CPU dies.

Changes in v4:
-Initialize cpu_smpboot notifier at presmp_init rather than init phase
 to cover the case where a secondary CPU dies beforehand the initcall
-Added newline before the return in cpu_smpboot_notifier_init()
-Fix indentation in cpu_smpboot_callback() definition
---
 xen/arch/arm/smpboot.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index ad1f6b751b..cf3a4ce659 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -89,6 +89,12 @@ static void setup_cpu_sibling_map(int cpu)
     cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, cpu));
 }
 
+static void remove_cpu_sibling_map(int cpu)
+{
+    free_cpumask_var(per_cpu(cpu_sibling_mask, cpu));
+    free_cpumask_var(per_cpu(cpu_core_mask, cpu));
+}
+
 void __init
 smp_clear_cpu_maps (void)
 {
@@ -499,6 +505,36 @@ void __cpu_die(unsigned int cpu)
     smp_mb();
 }
 
+static int cpu_smpboot_callback(struct notifier_block *nfb,
+                                unsigned long action,
+                                void *hcpu)
+{
+    unsigned int cpu = (unsigned long)hcpu;
+
+    switch ( action )
+    {
+    case CPU_DEAD:
+        remove_cpu_sibling_map(cpu);
+        break;
+    default:
+        break;
+    }
+
+    return NOTIFY_DONE;
+}
+
+static struct notifier_block cpu_smpboot_nfb = {
+    .notifier_call = cpu_smpboot_callback,
+};
+
+static int __init cpu_smpboot_notifier_init(void)
+{
+    register_cpu_notifier(&cpu_smpboot_nfb);
+
+    return 0;
+}
+presmp_initcall(cpu_smpboot_notifier_init);
+
 /*
  * Local variables:
  * mode: C
-- 
2.13.0


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