2 files changed, 16 insertions, 6 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index c83f51d6e359..32cd1acb7386 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -173,6 +173,7 @@ struct perf_counter {
         const struct hw_perf_counter_ops *hw_ops;
 
         enum perf_counter_active_state  state;
+        enum perf_counter_active_state  prev_state;
         atomic64_t                      count;
 
         struct perf_counter_hw_event    hw_event;
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index fcefb0a726f3..ad62965828d3 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -444,6 +444,7 @@ static void __perf_install_in_context(void *info)
 
         list_add_counter(counter, ctx);
         ctx->nr_counters++;
+        counter->prev_state = PERF_COUNTER_STATE_OFF;
 
         /*
          * Don't put the counter on if it is disabled or if
@@ -562,6 +563,7 @@ static void __perf_counter_enable(void *info)
         curr_rq_lock_irq_save(&flags);
         spin_lock(&ctx->lock);
 
+        counter->prev_state = counter->state;
         if (counter->state >= PERF_COUNTER_STATE_INACTIVE)
                 goto unlock;
         counter->state = PERF_COUNTER_STATE_INACTIVE;
@@ -733,6 +735,7 @@ group_sched_in(struct perf_counter *group_counter,
         if (ret)
                 return ret < 0 ? ret : 0;
 
+        group_counter->prev_state = group_counter->state;
         if (counter_sched_in(group_counter, cpuctx, ctx, cpu))
                 return -EAGAIN;
 
@@ -740,6 +743,7 @@ group_sched_in(struct perf_counter *group_counter,
          * Schedule in siblings as one group (if any):
          */
         list_for_each_entry(counter, &group_counter->sibling_list, list_entry) {
+                counter->prev_state = counter->state;
                 if (counter_sched_in(counter, cpuctx, ctx, cpu)) {
                         partial_group = counter;
                         goto group_error;
@@ -1398,9 +1402,9 @@ static void task_clock_perf_counter_read(struct perf_counter *counter)
 
 static int task_clock_perf_counter_enable(struct perf_counter *counter)
 {
-        u64 now = task_clock_perf_counter_val(counter, 0);
-
-        atomic64_set(&counter->hw.prev_count, now);
+        if (counter->prev_state <= PERF_COUNTER_STATE_OFF)
+                atomic64_set(&counter->hw.prev_count,
+                             task_clock_perf_counter_val(counter, 0));
 
         return 0;
 }
@@ -1455,7 +1459,8 @@ static void page_faults_perf_counter_read(struct perf_counter *counter)
 
 static int page_faults_perf_counter_enable(struct perf_counter *counter)
 {
-        atomic64_set(&counter->hw.prev_count, get_page_faults(counter));
+        if (counter->prev_state <= PERF_COUNTER_STATE_OFF)
+                atomic64_set(&counter->hw.prev_count, get_page_faults(counter));
         return 0;
 }
 
@@ -1501,7 +1506,9 @@ static void context_switches_perf_counter_read(struct perf_counter *counter)
 
 static int context_switches_perf_counter_enable(struct perf_counter *counter)
 {
-        atomic64_set(&counter->hw.prev_count, get_context_switches(counter));
+        if (counter->prev_state <= PERF_COUNTER_STATE_OFF)
+                atomic64_set(&counter->hw.prev_count,
+                             get_context_switches(counter));
         return 0;
 }
 
@@ -1547,7 +1554,9 @@ static void cpu_migrations_perf_counter_read(struct perf_counter *counter)
 
 static int cpu_migrations_perf_counter_enable(struct perf_counter *counter)
 {
-        atomic64_set(&counter->hw.prev_count, get_cpu_migrations(counter));
+        if (counter->prev_state <= PERF_COUNTER_STATE_OFF)
+                atomic64_set(&counter->hw.prev_count,
+                             get_cpu_migrations(counter));
         return 0;
 }