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Commit ff32504f authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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tracing/ftrace: don't insert TRACE_PRINT during selftests 



Impact: fix tracer selfstests false results

After setting a ftrace_printk somewhere in th kernel, I saw the
Function tracer selftest failing.

When a selftest occurs, the ring buffer is lurked to see if
some entries were inserted. But concurrent insertion such as
ftrace_printk could occured at the same time and could give
false positive or negative results.

This patch prevent prevent from TRACE_PRINT entries insertion
during selftests.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 970987be

kernel/trace/trace.c

+12 −1
Original line number Diff line number Diff line
@@ -44,6 +44,14 @@ 
unsigned long __read_mostly	tracing_max_latency = (cycle_t)ULONG_MAX;

unsigned long __read_mostly	tracing_thresh;



/* We need to change this state when a selftest is running.

 * A selftest will lurk into the ring-buffer to count the

 * entries inserted during the selftest although some concurrent

 * insertions into the ring-buffer such as ftrace_printk could occurred

 * at the same time, giving false positive or negative results.

 */

static atomic_t tracing_selftest_running = ATOMIC_INIT(0);



/* For tracers that don't implement custom flags */

static struct tracer_opt dummy_tracer_opt[] = {

	{ }
@@ -589,6 +597,8 @@ int register_tracer(struct tracer *type) 
		struct tracer *saved_tracer = current_trace;

		struct trace_array *tr = &global_trace;

		int i;



		atomic_set(&tracing_selftest_running, 1);

		/*

		 * Run a selftest on this tracer.

		 * Here we reset the trace buffer, and set the current
@@ -603,6 +613,7 @@ int register_tracer(struct tracer *type) 
		/* the test is responsible for initializing and enabling */

		pr_info("Testing tracer %s: ", type->name);

		ret = type->selftest(type, tr);

		atomic_set(&tracing_selftest_running, 0);

		/* the test is responsible for resetting too */

		current_trace = saved_tracer;

		if (ret) {
@@ -3594,7 +3605,7 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args) 
	unsigned long flags, irq_flags;

	int cpu, len = 0, size, pc;



	if (tracing_disabled)

	if (tracing_disabled || atomic_read(&tracing_selftest_running))

		return 0;



	pc = preempt_count();