Commit ff32504f authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
Browse files

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 <>
Acked-by: default avatarSteven Rostedt <>
Signed-off-by: default avatarIngo Molnar <>
parent 970987be
......@@ -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();
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