[PATCH 09/18] tracing: disable update max tracer while reading trace

[Steven Rostedt]

From: Steven Rostedt <srostedt@xxxxxxxxxx>

When reading the tracer from the trace file, updating the max latency
may corrupt the output. This patch disables the tracing of the max
latency while reading the trace file.

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index df2c9f7..e521f1e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -263,6 +263,9 @@ unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
 	TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
 	TRACE_ITER_GRAPH_TIME;
 
+static int trace_stop_count;
+static DEFINE_SPINLOCK(tracing_start_lock);
+
 /**
  * trace_wake_up - wake up tasks waiting for trace input
  *
@@ -442,6 +445,9 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 {
 	struct ring_buffer *buf = tr->buffer;
 
+	if (trace_stop_count)
+		return;
+
 	WARN_ON_ONCE(!irqs_disabled());
 	__raw_spin_lock(&ftrace_max_lock);
 
@@ -469,6 +475,9 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 {
 	int ret;
 
+	if (trace_stop_count)
+		return;
+
 	WARN_ON_ONCE(!irqs_disabled());
 	__raw_spin_lock(&ftrace_max_lock);
 
@@ -685,9 +694,6 @@ static void trace_init_cmdlines(void)
 	cmdline_idx = 0;
 }
 
-static int trace_stop_count;
-static DEFINE_SPINLOCK(tracing_start_lock);
-
 /**
  * ftrace_off_permanent - disable all ftrace code permanently
  *
-- 
1.6.3.3

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