tracing: Fix reset of time stamps during trace_clock changes
Alexander Z Lam [Sat, 3 Aug 2013 01:36:16 +0000 (18:36 -0700)]
commit 9457158bbc0ee04ecef76862d73eecd8076e9c7b upstream.

Fixed two issues with changing the timestamp clock with trace_clock:

 - The global buffer was reset on instance clock changes. Change this to pass
   the correct per-instance buffer
 - ftrace_now() is used to set buf->time_start in tracing_reset_online_cpus().
   This was incorrect because ftrace_now() used the global buffer's clock to
   return the current time. Change this to use buffer_ftrace_now() which
   returns the current time for the correct per-instance buffer.

Also removed tracing_reset_current() because it is not used anywhere

Link: http://lkml.kernel.org/r/1375493777-17261-2-git-send-email-azl@google.com

Signed-off-by: Alexander Z Lam <azl@google.com>
Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Alexander Z Lam <lambchop468@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/trace/trace.c

index b2aebd6..06a5bce 100644 (file)
@@ -232,20 +232,25 @@ int filter_current_check_discard(struct ring_buffer *buffer,
 }
 EXPORT_SYMBOL_GPL(filter_current_check_discard);
 
-cycle_t ftrace_now(int cpu)
+cycle_t buffer_ftrace_now(struct trace_buffer *buf, int cpu)
 {
        u64 ts;
 
        /* Early boot up does not have a buffer yet */
-       if (!global_trace.trace_buffer.buffer)
+       if (!buf->buffer)
                return trace_clock_local();
 
-       ts = ring_buffer_time_stamp(global_trace.trace_buffer.buffer, cpu);
-       ring_buffer_normalize_time_stamp(global_trace.trace_buffer.buffer, cpu, &ts);
+       ts = ring_buffer_time_stamp(buf->buffer, cpu);
+       ring_buffer_normalize_time_stamp(buf->buffer, cpu, &ts);
 
        return ts;
 }
 
+cycle_t ftrace_now(int cpu)
+{
+       return buffer_ftrace_now(&global_trace.trace_buffer, cpu);
+}
+
 /**
  * tracing_is_enabled - Show if global_trace has been disabled
  *
@@ -1194,7 +1199,7 @@ void tracing_reset_online_cpus(struct trace_buffer *buf)
        /* Make sure all commits have finished */
        synchronize_sched();
 
-       buf->time_start = ftrace_now(buf->cpu);
+       buf->time_start = buffer_ftrace_now(buf, buf->cpu);
 
        for_each_online_cpu(cpu)
                ring_buffer_reset_cpu(buffer, cpu);
@@ -1202,11 +1207,6 @@ void tracing_reset_online_cpus(struct trace_buffer *buf)
        ring_buffer_record_enable(buffer);
 }
 
-void tracing_reset_current(int cpu)
-{
-       tracing_reset(&global_trace.trace_buffer, cpu);
-}
-
 /* Must have trace_types_lock held */
 void tracing_reset_all_online_cpus(void)
 {
@@ -4647,12 +4647,12 @@ static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
         * New clock may not be consistent with the previous clock.
         * Reset the buffer so that it doesn't have incomparable timestamps.
         */
-       tracing_reset_online_cpus(&global_trace.trace_buffer);
+       tracing_reset_online_cpus(&tr->trace_buffer);
 
 #ifdef CONFIG_TRACER_MAX_TRACE
        if (tr->flags & TRACE_ARRAY_FL_GLOBAL && tr->max_buffer.buffer)
                ring_buffer_set_clock(tr->max_buffer.buffer, trace_clocks[i].func);
-       tracing_reset_online_cpus(&global_trace.max_buffer);
+       tracing_reset_online_cpus(&tr->max_buffer);
 #endif
 
        mutex_unlock(&trace_types_lock);