tracing/ftrace: change the type of the init() callback

Impact: extend the ->init() method with the ability to fail

This bring a way to know if the initialization of a tracer successed.
A tracer must return 0 on success and a traditional error (ie:
-ENOMEM) if it fails.

If a tracer fails to init, it is free to print a detailed warn. The
tracing api will not and switch to a new tracer will just return the
error from the init callback.

Note: this will be used for the return tracer.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 57 insertions, 9 deletions

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 5cb64ea061b5..88c8eb70f54a 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -71,6 +71,11 @@ static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
         return ret;
 }
 
+static inline void warn_failed_init_tracer(struct tracer *trace, int init_ret)
+{
+        printk(KERN_WARNING "Failed to init %s tracer, init returned %d\n",
+                trace->name, init_ret);
+}
 #ifdef CONFIG_FUNCTION_TRACER
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -111,7 +116,11 @@ int trace_selftest_startup_dynamic_tracing(struct tracer *trace,
         ftrace_set_filter(func_name, strlen(func_name), 1);
 
         /* enable tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                goto out;
+        }
 
         /* Sleep for a 1/10 of a second */
         msleep(100);
@@ -181,7 +190,12 @@ trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
         ftrace_enabled = 1;
         tracer_enabled = 1;
 
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                goto out;
+        }
+
         /* Sleep for a 1/10 of a second */
         msleep(100);
         /* stop the tracing. */
@@ -223,7 +237,12 @@ trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)
         int ret;
 
         /* start the tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                return ret;
+        }
+
         /* reset the max latency */
         tracing_max_latency = 0;
         /* disable interrupts for a bit */
@@ -272,7 +291,12 @@ trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr)
         }
 
         /* start the tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                return ret;
+        }
+
         /* reset the max latency */
         tracing_max_latency = 0;
         /* disable preemption for a bit */
@@ -321,7 +345,11 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
         }
 
         /* start the tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                goto out;
+        }
 
         /* reset the max latency */
         tracing_max_latency = 0;
@@ -449,7 +477,12 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
         wait_for_completion(&isrt);
 
         /* start the tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                return ret;
+        }
+
         /* reset the max latency */
         tracing_max_latency = 0;
 
@@ -505,7 +538,12 @@ trace_selftest_startup_sched_switch(struct tracer *trace, struct trace_array *tr
         int ret;
 
         /* start the tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                return ret;
+        }
+
         /* Sleep for a 1/10 of a second */
         msleep(100);
         /* stop the tracing. */
@@ -532,7 +570,12 @@ trace_selftest_startup_sysprof(struct tracer *trace, struct trace_array *tr)
         int ret;
 
         /* start the tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                return 0;
+        }
+
         /* Sleep for a 1/10 of a second */
         msleep(100);
         /* stop the tracing. */
@@ -554,7 +597,12 @@ trace_selftest_startup_branch(struct tracer *trace, struct trace_array *tr)
         int ret;
 
         /* start the tracing */
-        trace->init(tr);
+        ret = trace->init(tr);
+        if (ret) {
+                warn_failed_init_tracer(trace, ret);
+                return ret;
+        }
+
         /* Sleep for a 1/10 of a second */
         msleep(100);
         /* stop the tracing. */