perf/x86: Avoid kfree() in CPU_{STARTING,DYING}

On -rt kfree() can schedule, but CPU_{STARTING,DYING} should be
atomic. So use a list to defer kfree until CPU_{ONLINE,DEAD}.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: peterz@infradead.org
Cc: eranian@google.com
Cc: ak@linux.intel.com
Link: http://lkml.kernel.org/r/1366113067-3262-2-git-send-email-zheng.z.yan@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 75da9e1..50d4a1c 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -2622,6 +2622,21 @@ static void __init uncore_pci_exit(void)
        }
 }
 
+/* CPU hot plug/unplug are serialized by cpu_add_remove_lock mutex */
+static LIST_HEAD(boxes_to_free);
+
+static void __cpuinit uncore_kfree_boxes(void)
+{
+       struct intel_uncore_box *box;
+
+       while (!list_empty(&boxes_to_free)) {
+               box = list_entry(boxes_to_free.next,
+                                struct intel_uncore_box, list);
+               list_del(&box->list);
+               kfree(box);
+       }
+}
+
 static void __cpuinit uncore_cpu_dying(int cpu)
 {
        struct intel_uncore_type *type;
@@ -2636,7 +2651,7 @@ static void __cpuinit uncore_cpu_dying(int cpu)
                        box = *per_cpu_ptr(pmu->box, cpu);
                        *per_cpu_ptr(pmu->box, cpu) = NULL;
                        if (box && atomic_dec_and_test(&box->refcnt))
-                               kfree(box);
+                               list_add(&box->list, &boxes_to_free);
                }
        }
 }
@@ -2666,8 +2681,11 @@ static int __cpuinit uncore_cpu_starting(int cpu)
                                if (exist && exist->phys_id == phys_id) {
                                        atomic_inc(&exist->refcnt);
                                        *per_cpu_ptr(pmu->box, cpu) = exist;
-                                       kfree(box);
-                                       box = NULL;
+                                       if (box) {
+                                               list_add(&box->list,
+                                                        &boxes_to_free);
+                                               box = NULL;
+                                       }
                                        break;
                                }
                        }
@@ -2806,6 +2824,10 @@ static int
        case CPU_DYING:
                uncore_cpu_dying(cpu);
                break;
+       case CPU_ONLINE:
+       case CPU_DEAD:
+               uncore_kfree_boxes();
+               break;
        default:
                break;
        }