1 files changed, 20 insertions, 9 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 126a302c481c..656222fcf767 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -782,6 +782,10 @@ retry:
         raw_spin_unlock_irq(&ctx->lock);
 }
 
+#define MAX_INTERRUPTS (~0ULL)
+
+static void perf_log_throttle(struct perf_event *event, int enable);
+
 static int
 event_sched_in(struct perf_event *event,
                  struct perf_cpu_context *cpuctx,
@@ -794,6 +798,17 @@ event_sched_in(struct perf_event *event,
 
         event->state = PERF_EVENT_STATE_ACTIVE;
         event->oncpu = smp_processor_id();
+
+        /*
+         * Unthrottle events, since we scheduled we might have missed several
+         * ticks already, also for a heavily scheduling task there is little
+         * guarantee it'll get a tick in a timely manner.
+         */
+        if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
+                perf_log_throttle(event, 1);
+                event->hw.interrupts = 0;
+        }
+
         /*
          * The new state must be visible before we turn it on in the hardware:
          */
@@ -1596,10 +1611,6 @@ void __perf_event_task_sched_in(struct task_struct *task)
         }
 }
 
-#define MAX_INTERRUPTS (~0ULL)
-
-static void perf_log_throttle(struct perf_event *event, int enable);
-
 static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
 {
         u64 frequency = event->attr.sample_freq;
@@ -1901,11 +1912,12 @@ static void __perf_event_read(void *info)
                 return;
 
         raw_spin_lock(&ctx->lock);
-        update_context_time(ctx);
+        if (ctx->is_active)
+                update_context_time(ctx);
         update_event_times(event);
+        if (event->state == PERF_EVENT_STATE_ACTIVE)
+                event->pmu->read(event);
         raw_spin_unlock(&ctx->lock);
-
-        event->pmu->read(event);
 }
 
 static inline u64 perf_event_count(struct perf_event *event)
@@ -1999,8 +2011,7 @@ static int alloc_callchain_buffers(void)
          * accessed from NMI. Use a temporary manual per cpu allocation
          * until that gets sorted out.
          */
-        size = sizeof(*entries) + sizeof(struct perf_callchain_entry *) *
-                num_possible_cpus();
+        size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]);
 
         entries = kzalloc(size, GFP_KERNEL);
         if (!entries)