4 files changed, 38 insertions, 6 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index af9042977c08..f7488f44d26b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -660,6 +660,10 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 		return;
 
 	WARN_ON_ONCE(!irqs_disabled());
+	if (!current_trace->use_max_tr) {
+		WARN_ON_ONCE(1);
+		return;
+	}
 	arch_spin_lock(&ftrace_max_lock);
 
 	tr->buffer = max_tr.buffer;
@@ -686,6 +690,11 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 		return;
 
 	WARN_ON_ONCE(!irqs_disabled());
+	if (!current_trace->use_max_tr) {
+		WARN_ON_ONCE(1);
+		return;
+	}
+
 	arch_spin_lock(&ftrace_max_lock);
 
 	ftrace_disable_cpu();
@@ -2801,6 +2810,9 @@ static int tracing_resize_ring_buffer(unsigned long size)
 	if (ret < 0)
 		return ret;
 
+	if (!current_trace->use_max_tr)
+		goto out;
+
 	ret = ring_buffer_resize(max_tr.buffer, size);
 	if (ret < 0) {
 		int r;
@@ -2828,11 +2840,14 @@ static int tracing_resize_ring_buffer(unsigned long size)
 		return ret;
 	}
 
+	max_tr.entries = size;
+ out:
 	global_trace.entries = size;
 
 	return ret;
 }
 
+
 /**
  * tracing_update_buffers - used by tracing facility to expand ring buffers
  *
@@ -2893,12 +2908,26 @@ static int tracing_set_tracer(const char *buf)
 	trace_branch_disable();
 	if (current_trace && current_trace->reset)
 		current_trace->reset(tr);
-
+	if (current_trace && current_trace->use_max_tr) {
+		/*
+		 * We don't free the ring buffer. instead, resize it because
+		 * The max_tr ring buffer has some state (e.g. ring->clock) and
+		 * we want preserve it.
+		 */
+		ring_buffer_resize(max_tr.buffer, 1);
+		max_tr.entries = 1;
+	}
 	destroy_trace_option_files(topts);
 
 	current_trace = t;
 
 	topts = create_trace_option_files(current_trace);
+	if (current_trace->use_max_tr) {
+		ret = ring_buffer_resize(max_tr.buffer, global_trace.entries);
+		if (ret < 0)
+			goto out;
+		max_tr.entries = global_trace.entries;
+	}
 
 	if (t->init) {
 		ret = tracer_init(t, tr);
@@ -3480,7 +3509,6 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,
 	}
 
 	tracing_start();
-	max_tr.entries = global_trace.entries;
 	mutex_unlock(&trace_types_lock);
 
 	return cnt;
@@ -4578,16 +4606,14 @@ __init static int tracer_alloc_buffers(void)
 
 
 #ifdef CONFIG_TRACER_MAX_TRACE
-	max_tr.buffer = ring_buffer_alloc(ring_buf_size,
-					     TRACE_BUFFER_FLAGS);
+	max_tr.buffer = ring_buffer_alloc(1, TRACE_BUFFER_FLAGS);
 	if (!max_tr.buffer) {
 		printk(KERN_ERR "tracer: failed to allocate max ring buffer!\n");
 		WARN_ON(1);
 		ring_buffer_free(global_trace.buffer);
 		goto out_free_cpumask;
 	}
-	max_tr.entries = ring_buffer_size(max_tr.buffer);
-	WARN_ON(max_tr.entries != global_trace.entries);
+	max_tr.entries = 1;
 #endif
 
 	/* Allocate the first page for all buffers */
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 7778f067fc8b..cb629b3b108c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -276,6 +276,7 @@ struct tracer {
 	struct tracer		*next;
 	int			print_max;
 	struct tracer_flags	*flags;
+	int			use_max_tr;
 };
 
 
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 6fd486e0cef4..73a6b0601f2e 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -649,6 +649,7 @@ static struct tracer irqsoff_tracer __read_mostly =
 #endif
 	.open           = irqsoff_trace_open,
 	.close          = irqsoff_trace_close,
+	.use_max_tr	= 1,
 };
 # define register_irqsoff(trace) register_tracer(&trace)
 #else
@@ -681,6 +682,7 @@ static struct tracer preemptoff_tracer __read_mostly =
 #endif
 	.open		= irqsoff_trace_open,
 	.close		= irqsoff_trace_close,
+	.use_max_tr	= 1,
 };
 # define register_preemptoff(trace) register_tracer(&trace)
 #else
@@ -715,6 +717,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
 #endif
 	.open		= irqsoff_trace_open,
 	.close		= irqsoff_trace_close,
+	.use_max_tr	= 1,
 };
 
 # define register_preemptirqsoff(trace) register_tracer(&trace)
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index c9fd5bd02036..4086eae6e81b 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -382,6 +382,7 @@ static struct tracer wakeup_tracer __read_mostly =
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_wakeup,
 #endif
+	.use_max_tr	= 1,
 };
 
 static struct tracer wakeup_rt_tracer __read_mostly =
@@ -396,6 +397,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_wakeup,
 #endif
+	.use_max_tr	= 1,
 };
 
 __init static int init_wakeup_tracer(void)