1 files changed, 63 insertions, 17 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 54517a889791..7daf372e319a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -454,10 +454,6 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
         tr->buffer = max_tr.buffer;
         max_tr.buffer = buf;
 
-        ftrace_disable_cpu();
-        ring_buffer_reset(tr->buffer);
-        ftrace_enable_cpu();
-
         __update_max_tr(tr, tsk, cpu);
         __raw_spin_unlock(&ftrace_max_lock);
 }
@@ -483,7 +479,6 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 
         ftrace_disable_cpu();
 
-        ring_buffer_reset(max_tr.buffer);
         ret = ring_buffer_swap_cpu(max_tr.buffer, tr->buffer, cpu);
 
         ftrace_enable_cpu();
@@ -1374,6 +1369,37 @@ static void *s_next(struct seq_file *m, void *v, loff_t *pos)
         return ent;
 }
 
+static void tracing_iter_reset(struct trace_iterator *iter, int cpu)
+{
+        struct trace_array *tr = iter->tr;
+        struct ring_buffer_event *event;
+        struct ring_buffer_iter *buf_iter;
+        unsigned long entries = 0;
+        u64 ts;
+
+        tr->data[cpu]->skipped_entries = 0;
+
+        if (!iter->buffer_iter[cpu])
+                return;
+
+        buf_iter = iter->buffer_iter[cpu];
+        ring_buffer_iter_reset(buf_iter);
+
+        /*
+         * We could have the case with the max latency tracers
+         * that a reset never took place on a cpu. This is evident
+         * by the timestamp being before the start of the buffer.
+         */
+        while ((event = ring_buffer_iter_peek(buf_iter, &ts))) {
+                if (ts >= iter->tr->time_start)
+                        break;
+                entries++;
+                ring_buffer_read(buf_iter, NULL);
+        }
+
+        tr->data[cpu]->skipped_entries = entries;
+}
+
 /*
  * No necessary locking here. The worst thing which can
  * happen is loosing events consumed at the same time
@@ -1412,10 +1438,9 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 
                 if (cpu_file == TRACE_PIPE_ALL_CPU) {
                         for_each_tracing_cpu(cpu)
-                                ring_buffer_iter_reset(iter->buffer_iter[cpu]);
+                                tracing_iter_reset(iter, cpu);
                 } else
-                        ring_buffer_iter_reset(iter->buffer_iter[cpu_file]);
-
+                        tracing_iter_reset(iter, cpu_file);
 
                 ftrace_enable_cpu();
 
@@ -1464,16 +1489,32 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
         struct trace_array *tr = iter->tr;
         struct trace_array_cpu *data = tr->data[tr->cpu];
         struct tracer *type = current_trace;
-        unsigned long total;
-        unsigned long entries;
+        unsigned long entries = 0;
+        unsigned long total = 0;
+        unsigned long count;
         const char *name = "preemption";
+        int cpu;
 
         if (type)
                 name = type->name;
 
-        entries = ring_buffer_entries(iter->tr->buffer);
-        total = entries +
-                ring_buffer_overruns(iter->tr->buffer);
+
+        for_each_tracing_cpu(cpu) {
+                count = ring_buffer_entries_cpu(tr->buffer, cpu);
+                /*
+                 * If this buffer has skipped entries, then we hold all
+                 * entries for the trace and we need to ignore the
+                 * ones before the time stamp.
+                 */
+                if (tr->data[cpu]->skipped_entries) {
+                        count -= tr->data[cpu]->skipped_entries;
+                        /* total is the same as the entries */
+                        total += count;
+                } else
+                        total += count +
+                                ring_buffer_overrun_cpu(tr->buffer, cpu);
+                entries += count;
+        }
 
         seq_printf(m, "# %s latency trace v1.1.5 on %s\n",
                    name, UTS_RELEASE);
@@ -1534,6 +1575,9 @@ static void test_cpu_buff_start(struct trace_iterator *iter)
         if (cpumask_test_cpu(iter->cpu, iter->started))
                 return;
 
+        if (iter->tr->data[iter->cpu]->skipped_entries)
+                return;
+
         cpumask_set_cpu(iter->cpu, iter->started);
 
         /* Don't print started cpu buffer for the first entry of the trace */
@@ -1796,19 +1840,23 @@ __tracing_open(struct inode *inode, struct file *file)
         if (ring_buffer_overruns(iter->tr->buffer))
                 iter->iter_flags |= TRACE_FILE_ANNOTATE;
 
+        /* stop the trace while dumping */
+        tracing_stop();
+
         if (iter->cpu_file == TRACE_PIPE_ALL_CPU) {
                 for_each_tracing_cpu(cpu) {
 
                         iter->buffer_iter[cpu] =
                                 ring_buffer_read_start(iter->tr->buffer, cpu);
+                        tracing_iter_reset(iter, cpu);
                 }
         } else {
                 cpu = iter->cpu_file;
                 iter->buffer_iter[cpu] =
                                 ring_buffer_read_start(iter->tr->buffer, cpu);
+                tracing_iter_reset(iter, cpu);
         }
 
-        /* TODO stop tracer */
         ret = seq_open(file, &tracer_seq_ops);
         if (ret < 0) {
                 fail_ret = ERR_PTR(ret);
@@ -1818,9 +1866,6 @@ __tracing_open(struct inode *inode, struct file *file)
         m = file->private_data;
         m->private = iter;
 
-        /* stop the trace while dumping */
-        tracing_stop();
-
         mutex_unlock(&trace_types_lock);
 
         return iter;
@@ -1831,6 +1876,7 @@ __tracing_open(struct inode *inode, struct file *file)
                         ring_buffer_read_finish(iter->buffer_iter[cpu]);
         }
         free_cpumask_var(iter->started);
+        tracing_start();
  fail:
         mutex_unlock(&trace_types_lock);
         kfree(iter->trace);