1 files changed, 21 insertions, 3 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index bd1c35a4fbcc..db7b439d23ee 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5,7 +5,6 @@
  */
 #include <linux/ring_buffer.h>
 #include <linux/trace_clock.h>
-#include <linux/ftrace_irq.h>
 #include <linux/spinlock.h>
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
@@ -1429,6 +1428,17 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 }
 EXPORT_SYMBOL_GPL(ring_buffer_resize);
 
+void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
+{
+        mutex_lock(&buffer->mutex);
+        if (val)
+                buffer->flags |= RB_FL_OVERWRITE;
+        else
+                buffer->flags &= ~RB_FL_OVERWRITE;
+        mutex_unlock(&buffer->mutex);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
+
 static inline void *
 __rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
 {
@@ -2162,11 +2172,19 @@ rb_reserve_next_event(struct ring_buffer *buffer,
         if (likely(ts >= cpu_buffer->write_stamp)) {
                 delta = diff;
                 if (unlikely(test_time_stamp(delta))) {
+                        int local_clock_stable = 1;
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+                        local_clock_stable = sched_clock_stable;
+#endif
                         WARN_ONCE(delta > (1ULL << 59),
-                                  KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n",
+                                  KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
                                   (unsigned long long)delta,
                                   (unsigned long long)ts,
-                                  (unsigned long long)cpu_buffer->write_stamp);
+                                  (unsigned long long)cpu_buffer->write_stamp,
+                                  local_clock_stable ? "" :
+                                  "If you just came from a suspend/resume,\n"
+                                  "please switch to the trace global clock:\n"
+                                  "  echo global > /sys/kernel/debug/tracing/trace_clock\n");
                         add_timestamp = 1;
                 }
         }