tracing/events: Add trace_event boot option
We already have ftrace= boot option, and this adds a similar
boot option for trace events, so allow trace events to be
enabled at boot, for boot debugging purpose.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A4ACE29.3010407@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index d3f41db..2582e7a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2478,6 +2478,11 @@
trace_buf_size=nn[KMG]
[FTRACE] will set tracing buffer size.
+ trace_event=[event-list]
+ [FTRACE] Set and start specified trace events in order
+ to facilitate early boot debugging.
+ See also Documentation/trace/events.txt
+
trix= [HW,OSS] MediaTrix AudioTrix Pro
Format:
<io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index f157d75..2bcc8d4 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -83,6 +83,15 @@
X - there is a mixture of events enabled and disabled
? - this file does not affect any event
+2.3 Boot option
+---------------
+
+In order to facilitate early boot debugging, use boot option:
+
+ trace_event=[event-list]
+
+The format of this boot option is the same as described in section 2.1.
+
3. Defining an event-enabled tracepoint
=======================================
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3aa0a0d..bdb3afc 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -49,7 +49,7 @@
* On boot up, the ring buffer is set to the minimum size, so that
* we do not waste memory on systems that are not using tracing.
*/
-static int ring_buffer_expanded;
+int ring_buffer_expanded;
/*
* We need to change this state when a selftest is running.
@@ -63,7 +63,7 @@
/*
* If a tracer is running, we do not want to run SELFTEST.
*/
-static bool __read_mostly tracing_selftest_disabled;
+bool __read_mostly tracing_selftest_disabled;
/* For tracers that don't implement custom flags */
static struct tracer_opt dummy_tracer_opt[] = {
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 3548ae5..52eb0d8 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -517,6 +517,9 @@
extern int DYN_FTRACE_TEST_NAME(void);
#endif
+extern int ring_buffer_expanded;
+extern bool tracing_selftest_disabled;
+
#ifdef CONFIG_FTRACE_STARTUP_TEST
extern int trace_selftest_startup_function(struct tracer *trace,
struct trace_array *tr);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 53c8fd3..fecac13 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -17,6 +17,8 @@
#include <linux/ctype.h>
#include <linux/delay.h>
+#include <asm/setup.h>
+
#include "trace_output.h"
#define TRACE_SYSTEM "TRACE_SYSTEM"
@@ -1133,6 +1135,18 @@
extern struct ftrace_event_call __start_ftrace_events[];
extern struct ftrace_event_call __stop_ftrace_events[];
+static char bootup_event_buf[COMMAND_LINE_SIZE] __initdata;
+
+static __init int setup_trace_event(char *str)
+{
+ strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);
+ ring_buffer_expanded = 1;
+ tracing_selftest_disabled = 1;
+
+ return 1;
+}
+__setup("trace_event=", setup_trace_event);
+
static __init int event_trace_init(void)
{
struct ftrace_event_call *call;
@@ -1140,6 +1154,8 @@
struct dentry *entry;
struct dentry *d_events;
int ret;
+ char *buf = bootup_event_buf;
+ char *token;
d_tracer = tracing_init_dentry();
if (!d_tracer)
@@ -1185,6 +1201,19 @@
&ftrace_event_format_fops);
}
+ while (true) {
+ token = strsep(&buf, ",");
+
+ if (!token)
+ break;
+ if (!*token)
+ continue;
+
+ ret = ftrace_set_clr_event(token, 1);
+ if (ret)
+ pr_warning("Failed to enable trace event: %s\n", token);
+ }
+
ret = register_module_notifier(&trace_module_nb);
if (ret)
pr_warning("Failed to register trace events module notifier\n");
@@ -1392,10 +1421,10 @@
static __init int event_trace_self_tests_init(void)
{
-
- event_trace_self_tests();
-
- event_trace_self_test_with_function();
+ if (!tracing_selftest_disabled) {
+ event_trace_self_tests();
+ event_trace_self_test_with_function();
+ }
return 0;
}