perfcounters: fix task clock counter

Impact: bugfix

Update the task clock counter to the new math.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 23 insertions, 4 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index f5e81dd193d1..1f81cde0dc43 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -850,17 +850,36 @@ static const struct hw_perf_counter_ops perf_ops_cpu_clock = {
         .hw_perf_counter_read           = cpu_clock_perf_counter_read,
 };
 
-static void task_clock_perf_counter_enable(struct perf_counter *counter)
+static void task_clock_perf_counter_update(struct perf_counter *counter)
 {
+        u64 prev, now;
+        s64 delta;
+
+        prev = atomic64_read(&counter->hw.prev_count);
+        now = current->se.sum_exec_runtime;
+
+        atomic64_set(&counter->hw.prev_count, now);
+
+        delta = now - prev;
+        if (WARN_ON_ONCE(delta < 0))
+                delta = 0;
+
+        atomic64_add(delta, &counter->count);
 }
 
-static void task_clock_perf_counter_disable(struct perf_counter *counter)
+static void task_clock_perf_counter_read(struct perf_counter *counter)
 {
+        task_clock_perf_counter_update(counter);
 }
 
-static void task_clock_perf_counter_read(struct perf_counter *counter)
+static void task_clock_perf_counter_enable(struct perf_counter *counter)
+{
+        atomic64_set(&counter->hw.prev_count, current->se.sum_exec_runtime);
+}
+
+static void task_clock_perf_counter_disable(struct perf_counter *counter)
 {
-        atomic64_set(&counter->count, current->se.sum_exec_runtime);
+        task_clock_perf_counter_update(counter);
 }
 
 static const struct hw_perf_counter_ops perf_ops_task_clock = {