tracing/core: drop the old trace_printk() implementation in favour of trace_bprintk()

Impact: faster and lighter tracing

Now that we have trace_bprintk() which is faster and consume lesser
memory than trace_printk() and has the same purpose, we can now drop
the old implementation in favour of the binary one from trace_bprintk(),
which means we move all the implementation of trace_bprintk() to
trace_printk(), so the Api doesn't change except that we must now use
trace_seq_bprintk() to print the TRACE_PRINT entries.

Some changes result of this:

- Previously, trace_bprintk depended of a single tracer and couldn't
  work without. This tracer has been dropped and the whole implementation
  of trace_printk() (like the module formats management) is now integrated
  in the tracing core (comes with CONFIG_TRACING), though we keep the file
  trace_printk (previously trace_bprintk.c) where we can find the module
  management. Thus we don't overflow trace.c

- changes some parts to use trace_seq_bprintk() to print TRACE_PRINT entries.

- change a bit trace_printk/trace_vprintk macros to support non-builtin formats
  constants, and fix 'const' qualifiers warnings. But this is all transparent for
  developers.

- etc...

V2:

- Rebase against last changes
- Fix mispell on the changelog

V3:

- Rebase against last changes (moving trace_printk() to kernel.h)

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1236356510-8381-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/ftrace.h

@@ -223,31 +223,6 @@ extern int ftrace_make_nop(struct module *mod,
  */
 extern int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr);
 
-#ifdef CONFIG_TRACE_BPRINTK
-extern int trace_vbprintk(unsigned long ip, const char *fmt, va_list args);
-extern int __trace_bprintk(unsigned long ip, const char *fmt, ...)
-		__attribute__ ((format (printf, 2, 3)));
-
-static inline void  ____trace_bprintk_check_format(const char *fmt, ...)
-		__attribute__ ((format (printf, 1, 2)));
-static inline void ____trace_bprintk_check_format(const char *fmt, ...) {}
-#define __trace_bprintk_check_format(fmt, args...)			\
-do {									\
-	if (0)								\
-		____trace_bprintk_check_format(fmt, ##args);		\
-} while (0)
-
-#define trace_bprintk(fmt, args...)					\
-do {									\
-	static char *__attribute__((section("__trace_bprintk_fmt")))	\
-			trace_bprintk_fmt = fmt;			\
-	__trace_bprintk_check_format(fmt, ##args);			\
-	__trace_bprintk(_THIS_IP_, trace_bprintk_fmt, ##args);	\
-} while (0)
-#else
-#define trace_bprintk trace_printk
-#endif
-
 /* May be defined in arch */
 extern int ftrace_arch_read_dyn_info(char *buf, int size);
 

include/linux/kernel.h

@@ -423,6 +423,16 @@ extern void ftrace_off_permanent(void);
 extern void
 ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
 
+static inline void __attribute__ ((format (printf, 1, 2)))
+____trace_printk_check_format(const char *fmt, ...)
+{
+}
+#define __trace_printk_check_format(fmt, args...)			\
+do {									\
+	if (0)								\
+		____trace_printk_check_format(fmt, ##args);		\
+} while (0)
+
 /**
  * trace_printk - printf formatting in the ftrace buffer
  * @fmt: the printf format for printing
@@ -439,13 +449,31 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
  * Please refrain from leaving trace_printks scattered around in
  * your code.
  */
-# define trace_printk(fmt...) __trace_printk(_THIS_IP_, fmt)
+
+#define trace_printk(fmt, args...)					\
+do {									\
+	static const char *trace_printk_fmt				\
+	__attribute__((section("__trace_printk_fmt")));			\
+	trace_printk_fmt = fmt;					\
+	__trace_printk_check_format(fmt, ##args);			\
+	__trace_printk(_THIS_IP_, trace_printk_fmt, ##args);		\
+} while (0)
+
 extern int
 __trace_printk(unsigned long ip, const char *fmt, ...)
 	__attribute__ ((format (printf, 2, 3)));
-# define ftrace_vprintk(fmt, ap) __trace_printk(_THIS_IP_, fmt, ap)
+
+#define ftrace_vprintk(fmt, vargs)					\
+do {									\
+	static const char *trace_printk_fmt				\
+	__attribute__((section("__trace_printk_fmt")));			\
+	trace_printk_fmt = fmt;					\
+	__ftrace_vprintk(_THIS_IP_, trace_printk_fmt, vargs);		\
+} while (0)
+
 extern int
 __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
+
 extern void ftrace_dump(void);
 #else
 static inline void
@@ -467,7 +495,7 @@ ftrace_vprintk(const char *fmt, va_list ap)
 	return 0;
 }
 static inline void ftrace_dump(void) { }
-#endif
+#endif /* CONFIG_TRACING */
 
 /*
  *      Display an IP address in readable format.

include/linux/module.h

@@ -329,7 +329,7 @@ struct module
 	unsigned int num_tracepoints;
 #endif
 
-#ifdef CONFIG_TRACE_BPRINTK
+#ifdef CONFIG_TRACING
 	const char **trace_bprintk_fmt_start;
 	unsigned int num_trace_bprintk_fmt;
 #endif

kernel/trace/Kconfig

@@ -52,6 +52,7 @@ config TRACING
 	select STACKTRACE if STACKTRACE_SUPPORT
 	select TRACEPOINTS
 	select NOP_TRACER
+	select BINARY_PRINTF
 
 #
 # Minimum requirements an architecture has to meet for us to
@@ -97,12 +98,6 @@ config FUNCTION_GRAPH_TRACER
 	  This is done by setting the current return address on the current
 	  task structure into a stack of calls.
 
-config TRACE_BPRINTK
-	bool "Binary printk for tracing"
-	default y
-	depends on TRACING
-	select BINARY_PRINTF
-
 config IRQSOFF_TRACER
 	bool "Interrupts-off Latency Tracer"
 	default n

kernel/trace/Makefile

@@ -22,7 +22,7 @@ obj-$(CONFIG_TRACING) += trace.o
 obj-$(CONFIG_TRACING) += trace_clock.o
 obj-$(CONFIG_TRACING) += trace_output.o
 obj-$(CONFIG_TRACING) += trace_stat.o
-obj-$(CONFIG_TRACE_BPRINTK) += trace_bprintk.o
+obj-$(CONFIG_TRACING) += trace_printk.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_SYSPROF_TRACER) += trace_sysprof.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o

kernel/trace/trace.c

@@ -1169,6 +1169,67 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
+
+/**
+ * trace_vprintk - write binary msg to tracing buffer
+ *
+ */
+int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
+{
+	static DEFINE_SPINLOCK(trace_buf_lock);
+	static u32 trace_buf[TRACE_BUF_SIZE];
+
+	struct ring_buffer_event *event;
+	struct trace_array *tr = &global_trace;
+	struct trace_array_cpu *data;
+	struct print_entry *entry;
+	unsigned long flags;
+	int resched;
+	int cpu, len = 0, size, pc;
+
+	if (unlikely(tracing_selftest_running || tracing_disabled))
+		return 0;
+
+	/* Don't pollute graph traces with trace_vprintk internals */
+	pause_graph_tracing();
+
+	pc = preempt_count();
+	resched = ftrace_preempt_disable();
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+
+	if (unlikely(atomic_read(&data->disabled)))
+		goto out;
+
+	spin_lock_irqsave(&trace_buf_lock, flags);
+	len = vbin_printf(trace_buf, TRACE_BUF_SIZE, fmt, args);
+
+	if (len > TRACE_BUF_SIZE || len < 0)
+		goto out_unlock;
+
+	size = sizeof(*entry) + sizeof(u32) * len;
+	event = trace_buffer_lock_reserve(tr, TRACE_PRINT, size, flags, pc);
+	if (!event)
+		goto out_unlock;
+	entry = ring_buffer_event_data(event);
+	entry->ip			= ip;
+	entry->depth			= depth;
+	entry->fmt			= fmt;
+
+	memcpy(entry->buf, trace_buf, sizeof(u32) * len);
+	ring_buffer_unlock_commit(tr->buffer, event);
+
+out_unlock:
+	spin_unlock_irqrestore(&trace_buf_lock, flags);
+
+out:
+	ftrace_preempt_enable(resched);
+	unpause_graph_tracing();
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(trace_vprintk);
+
 enum trace_file_type {
 	TRACE_FILE_LAT_FMT	= 1,
 	TRACE_FILE_ANNOTATE	= 2,
@@ -1564,7 +1625,7 @@ static enum print_line_t print_printk_msg_only(struct trace_iterator *iter)
 
 	trace_assign_type(field, entry);
 
-	ret = trace_seq_printf(s, "%s", field->buf);
+	ret = trace_seq_bprintf(s, field->fmt, field->buf);
 	if (!ret)
 		return TRACE_TYPE_PARTIAL_LINE;
 
@@ -3714,155 +3775,6 @@ static __init int tracer_init_debugfs(void)
 	return 0;
 }
 
-int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
-{
-	static raw_spinlock_t trace_buf_lock = __RAW_SPIN_LOCK_UNLOCKED;
-	static char trace_buf[TRACE_BUF_SIZE];
-
-	struct ring_buffer_event *event;
-	struct trace_array *tr = &global_trace;
-	struct trace_array_cpu *data;
-	int cpu, len = 0, size, pc;
-	struct print_entry *entry;
-	unsigned long irq_flags;
-
-	if (tracing_disabled || tracing_selftest_running)
-		return 0;
-
-	pc = preempt_count();
-	preempt_disable_notrace();
-	cpu = raw_smp_processor_id();
-	data = tr->data[cpu];
-
-	if (unlikely(atomic_read(&data->disabled)))
-		goto out;
-
-	pause_graph_tracing();
-	raw_local_irq_save(irq_flags);
-	__raw_spin_lock(&trace_buf_lock);
-	len = vsnprintf(trace_buf, TRACE_BUF_SIZE, fmt, args);
-
-	len = min(len, TRACE_BUF_SIZE-1);
-	trace_buf[len] = 0;
-
-	size = sizeof(*entry) + len + 1;
-	event = trace_buffer_lock_reserve(tr, TRACE_PRINT, size, irq_flags, pc);
-	if (!event)
-		goto out_unlock;
-	entry = ring_buffer_event_data(event);
-	entry->ip			= ip;
-	entry->depth			= depth;
-
-	memcpy(&entry->buf, trace_buf, len);
-	entry->buf[len] = 0;
-	ring_buffer_unlock_commit(tr->buffer, event);
-
- out_unlock:
-	__raw_spin_unlock(&trace_buf_lock);
-	raw_local_irq_restore(irq_flags);
-	unpause_graph_tracing();
- out:
-	preempt_enable_notrace();
-
-	return len;
-}
-EXPORT_SYMBOL_GPL(trace_vprintk);
-
-int __trace_printk(unsigned long ip, const char *fmt, ...)
-{
-	int ret;
-	va_list ap;
-
-	if (!(trace_flags & TRACE_ITER_PRINTK))
-		return 0;
-
-	va_start(ap, fmt);
-	ret = trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
-	va_end(ap);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(__trace_printk);
-
-int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
-{
-	if (!(trace_flags & TRACE_ITER_PRINTK))
-		return 0;
-
-	return trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
-}
-EXPORT_SYMBOL_GPL(__ftrace_vprintk);
-
-/**
- * trace_vbprintk - write binary msg to tracing buffer
- *
- * Caller must insure @fmt are valid when msg is in tracing buffer.
- */
-int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
-{
-	static DEFINE_SPINLOCK(trace_buf_lock);
-	static u32 trace_buf[TRACE_BUF_SIZE];
-
-	struct ring_buffer_event *event;
-	struct trace_array *tr = &global_trace;
-	struct trace_array_cpu *data;
-	struct bprintk_entry *entry;
-	unsigned long flags;
-	int resched;
-	int cpu, len = 0, size, pc;
-
-	if (tracing_disabled || !trace_bprintk_enable)
-		return 0;
-
-	pc = preempt_count();
-	resched = ftrace_preempt_disable();
-	cpu = raw_smp_processor_id();
-	data = tr->data[cpu];
-
-	if (unlikely(atomic_read(&data->disabled)))
-		goto out;
-
-	spin_lock_irqsave(&trace_buf_lock, flags);
-	len = vbin_printf(trace_buf, TRACE_BUF_SIZE, fmt, args);
-
-	if (len > TRACE_BUF_SIZE || len < 0)
-		goto out_unlock;
-
-	size = sizeof(*entry) + sizeof(u32) * len;
-	event = trace_buffer_lock_reserve(tr, TRACE_BPRINTK, size, flags, pc);
-	if (!event)
-		goto out_unlock;
-	entry = ring_buffer_event_data(event);
-	entry->ip			= ip;
-	entry->fmt			= fmt;
-
-	memcpy(entry->buf, trace_buf, sizeof(u32) * len);
-	ring_buffer_unlock_commit(tr->buffer, event);
-
-out_unlock:
-	spin_unlock_irqrestore(&trace_buf_lock, flags);
-
-out:
-	ftrace_preempt_enable(resched);
-
-	return len;
-}
-EXPORT_SYMBOL_GPL(trace_vbprintk);
-
-int __trace_bprintk(unsigned long ip, const char *fmt, ...)
-{
-	int ret;
-	va_list ap;
-
-	if (!fmt)
-		return 0;
-
-	va_start(ap, fmt);
-	ret = trace_vbprintk(ip, fmt, ap);
-	va_end(ap);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(__trace_bprintk);
-
 static int trace_panic_handler(struct notifier_block *this,
 			       unsigned long event, void *unused)
 {

kernel/trace/trace.h

@@ -20,7 +20,6 @@ enum trace_type {
 	TRACE_WAKE,
 	TRACE_STACK,
 	TRACE_PRINT,
-	TRACE_BPRINTK,
 	TRACE_SPECIAL,
 	TRACE_MMIO_RW,
 	TRACE_MMIO_MAP,
@@ -120,16 +119,10 @@ struct userstack_entry {
  */
 struct print_entry {
 	struct trace_entry	ent;
-	unsigned long		ip;
+	unsigned long 		ip;
 	int			depth;
-	char			buf[];
-};
-
-struct bprintk_entry {
-	struct trace_entry ent;
-	unsigned long ip;
-	const char *fmt;
-	u32 buf[];
+	const char		*fmt;
+	u32 			buf[];
 };
 #ifdef CONFIG_TRACE_BPRINTK
 extern int trace_bprintk_enable;
@@ -296,7 +289,6 @@ extern void __ftrace_bad_type(void);
 		IF_ASSIGN(var, ent, struct stack_entry, TRACE_STACK);	\
 		IF_ASSIGN(var, ent, struct userstack_entry, TRACE_USER_STACK);\
 		IF_ASSIGN(var, ent, struct print_entry, TRACE_PRINT);	\
-		IF_ASSIGN(var, ent, struct bprintk_entry, TRACE_BPRINTK);\
 		IF_ASSIGN(var, ent, struct special_entry, 0);		\
 		IF_ASSIGN(var, ent, struct trace_mmiotrace_rw,		\
 			  TRACE_MMIO_RW);				\

kernel/trace/trace_functions_graph.c

@@ -742,7 +742,11 @@ print_graph_comment(struct print_entry *trace, struct trace_seq *s,
 		}
 
 	/* The comment */
-	ret = trace_seq_printf(s, "/* %s", trace->buf);
+	ret = trace_seq_printf(s, "/* ");
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	ret = trace_seq_bprintf(s, trace->fmt, trace->buf);
 	if (!ret)
 		return TRACE_TYPE_PARTIAL_LINE;
 

kernel/trace/trace_mmiotrace.c

@@ -254,15 +254,18 @@ static enum print_line_t mmio_print_mark(struct trace_iterator *iter)
 {
 	struct trace_entry *entry = iter->ent;
 	struct print_entry *print = (struct print_entry *)entry;
-	const char *msg		= print->buf;
 	struct trace_seq *s	= &iter->seq;
 	unsigned long long t	= ns2usecs(iter->ts);
-	unsigned long usec_rem	= do_div(t, 1000000ULL);
+	unsigned long usec_rem	= do_div(t, USEC_PER_SEC);
 	unsigned secs		= (unsigned long)t;
 	int ret;
 
 	/* The trailing newline must be in the message. */
-	ret = trace_seq_printf(s, "MARK %u.%06lu %s", secs, usec_rem, msg);
+	ret = trace_seq_printf(s, "MARK %u.%06lu ", secs, usec_rem);
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	ret = trace_seq_bprintf(s, print->fmt, print->buf);
 	if (!ret)
 		return TRACE_TYPE_PARTIAL_LINE;
 

kernel/trace/trace_output.c

@@ -53,8 +53,7 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 	return len;
 }
 
-static int
-trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
+int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
 {
 	int len = (PAGE_SIZE - 1) - s->len;
 	int ret;
@@ -834,54 +833,12 @@ static struct trace_event trace_user_stack_event = {
 };
 
 /* TRACE_PRINT */
-static enum print_line_t trace_print_print(struct trace_iterator *iter,
-					   int flags)
-{
-	struct print_entry *field;
-	struct trace_seq *s = &iter->seq;
-
-	trace_assign_type(field, iter->ent);
-
-	if (!seq_print_ip_sym(s, field->ip, flags))
-		goto partial;
-
-	if (!trace_seq_printf(s, ": %s", field->buf))
-		goto partial;
-
-	return TRACE_TYPE_HANDLED;
-
- partial:
-	return TRACE_TYPE_PARTIAL_LINE;
-}
-
-static enum print_line_t trace_print_raw(struct trace_iterator *iter, int flags)
-{
-	struct print_entry *field;
-
-	trace_assign_type(field, iter->ent);
-
-	if (!trace_seq_printf(&iter->seq, "# %lx %s", field->ip, field->buf))
-		goto partial;
-
-	return TRACE_TYPE_HANDLED;
-
- partial:
-	return TRACE_TYPE_PARTIAL_LINE;
-}
-
-static struct trace_event trace_print_event = {
-	.type	 	= TRACE_PRINT,
-	.trace		= trace_print_print,
-	.raw		= trace_print_raw,
-};
-
-/* TRACE_BPRINTK */
 static enum print_line_t
-trace_bprintk_print(struct trace_iterator *iter, int flags)
+trace_print_print(struct trace_iterator *iter, int flags)
 {
 	struct trace_entry *entry = iter->ent;
 	struct trace_seq *s = &iter->seq;
-	struct bprintk_entry *field;
+	struct print_entry *field;
 
 	trace_assign_type(field, entry);
 
@@ -900,14 +857,13 @@ trace_bprintk_print(struct trace_iterator *iter, int flags)
 	return TRACE_TYPE_PARTIAL_LINE;
 }
 
-static enum print_line_t
-trace_bprintk_raw(struct trace_iterator *iter, int flags)
+
+static enum print_line_t trace_print_raw(struct trace_iterator *iter, int flags)
 {
-	struct trace_entry *entry = iter->ent;
+	struct print_entry *field;
 	struct trace_seq *s = &iter->seq;
-	struct bprintk_entry *field;
 
-	trace_assign_type(field, entry);
+	trace_assign_type(field, iter->ent);
 
 	if (!trace_seq_printf(s, ": %lx : ", field->ip))
 		goto partial;
@@ -921,12 +877,11 @@ trace_bprintk_raw(struct trace_iterator *iter, int flags)
 	return TRACE_TYPE_PARTIAL_LINE;
 }
 
-static struct trace_event trace_bprintk_event = {
-	.type	 	= TRACE_BPRINTK,
-	.trace		= trace_bprintk_print,
-	.raw		= trace_bprintk_raw,
-	.hex		= trace_nop_print,
-	.binary		= trace_nop_print,
+
+static struct trace_event trace_print_event = {
+	.type	 	= TRACE_PRINT,
+	.trace		= trace_print_print,
+	.raw		= trace_print_raw,
 };
 
 static struct trace_event *events[] __initdata = {
@@ -937,7 +892,6 @@ static struct trace_event *events[] __initdata = {
 	&trace_stack_event,
 	&trace_user_stack_event,
 	&trace_print_event,
-	&trace_bprintk_event,
 	NULL
 };
 

kernel/trace/trace_output.h

@@ -18,6 +18,8 @@ struct trace_event {
 extern int trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 	__attribute__ ((format (printf, 2, 3)));
 extern int
+trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary);
+extern int
 seq_print_ip_sym(struct trace_seq *s, unsigned long ip,
 		unsigned long sym_flags);
 extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,

kernel/trace/trace_bprintk.c → kernel/trace/trace_printk.c

@@ -21,31 +21,20 @@
 
 #ifdef CONFIG_MODULES
 
-/* binary printk basic */
-static DEFINE_MUTEX(btrace_mutex);
 /*
- * modules trace_bprintk()'s formats are autosaved in struct trace_bprintk_fmt
+ * modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt
  * which are queued on trace_bprintk_fmt_list.
  */
 static LIST_HEAD(trace_bprintk_fmt_list);
 
+/* serialize accesses to trace_bprintk_fmt_list */
+static DEFINE_MUTEX(btrace_mutex);
+
 struct trace_bprintk_fmt {
 	struct list_head list;
 	char fmt[0];
 };
 
-
-static inline void lock_btrace(void)
-{
-	mutex_lock(&btrace_mutex);
-}
-
-static inline void unlock_btrace(void)
-{
-	mutex_unlock(&btrace_mutex);
-}
-
-
 static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
 {
 	struct trace_bprintk_fmt *pos;
@@ -60,7 +49,8 @@ static
 void hold_module_trace_bprintk_format(const char **start, const char **end)
 {
 	const char **iter;
-	lock_btrace();
+
+	mutex_lock(&btrace_mutex);
 	for (iter = start; iter < end; iter++) {
 		struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
 		if (tb_fmt) {
@@ -77,7 +67,7 @@ void hold_module_trace_bprintk_format(const char **start, const char **end)
 		} else
 			*iter = NULL;
 	}
-	unlock_btrace();
+	mutex_unlock(&btrace_mutex);
 }
 
 static int module_trace_bprintk_format_notify(struct notifier_block *self,
@@ -109,46 +99,40 @@ struct notifier_block module_trace_bprintk_format_nb = {
 	.notifier_call = module_trace_bprintk_format_notify,
 };
 
-/* events tracer */
-int trace_bprintk_enable;
+int __trace_printk(unsigned long ip, const char *fmt, ...)
+ {
+	int ret;
+	va_list ap;
 
-static void start_bprintk_trace(struct trace_array *tr)
-{
-	tracing_reset_online_cpus(tr);
-	trace_bprintk_enable = 1;
-}
+	if (unlikely(!fmt))
+		return 0;
 
-static void stop_bprintk_trace(struct trace_array *tr)
-{
-	trace_bprintk_enable = 0;
-	tracing_reset_online_cpus(tr);
+	if (!(trace_flags & TRACE_ITER_PRINTK))
+		return 0;
+
+	va_start(ap, fmt);
+	ret = trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
+	va_end(ap);
+	return ret;
 }
+EXPORT_SYMBOL_GPL(__trace_printk);
 
-static int init_bprintk_trace(struct trace_array *tr)
-{
-	start_bprintk_trace(tr);
-	return 0;
+int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
+ {
+	if (unlikely(!fmt))
+		return 0;
+
+	if (!(trace_flags & TRACE_ITER_PRINTK))
+		return 0;
+
+	return trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
 }
+EXPORT_SYMBOL_GPL(__ftrace_vprintk);
 
-static struct tracer bprintk_trace __read_mostly =
-{
-	.name	     = "events",
-	.init	     = init_bprintk_trace,
-	.reset	     = stop_bprintk_trace,
-	.start	     = start_bprintk_trace,
-	.stop	     = stop_bprintk_trace,
-};
 
-static __init int init_bprintk(void)
+static __init int init_trace_printk(void)
 {
-	int ret = register_module_notifier(&module_trace_bprintk_format_nb);
-	if (ret)
-		return ret;
-
-	ret = register_tracer(&bprintk_trace);
-	if (ret)
-		unregister_module_notifier(&module_trace_bprintk_format_nb);
-	return ret;
+	return register_module_notifier(&module_trace_bprintk_format_nb);
 }
 
-device_initcall(init_bprintk);
+early_initcall(init_trace_printk);