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>

1 files changed, 25 insertions, 3 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 75da9e18b128..50d4a1c58106 100644
--- 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;
         }