tracing/function-graph-tracer: handle ftrace_printk entries

Handle the TRACE_PRINT entries from the function grapg tracer
and output them as a C comment just below the function that called
it, as if it was a comment inside this function.

Example with an ftrace_printk inside might_sleep() function:

void __might_sleep(char *file, int line)
{
	static unsigned long prev_jiffy;	/* ratelimiting */

	ftrace_printk("Hi I'm a comment in might_sleep() :-)");

A chunk of a resulting trace:

 0)               |        _reiserfs_free_block() {
 0)               |          reiserfs_read_bitmap_block() {
 0)               |            __bread() {
 0)               |              __getblk() {
 0)               |                __find_get_block() {
 0)   0.698 us    |                  mark_page_accessed();
 0)   2.267 us    |                }
 0)               |                __might_sleep() {
 0)               |                  /* Hi I'm a comment in might_sleep() :-) */
 0)   1.321 us    |                }
 0)   5.872 us    |              }
 0)   7.313 us    |            }
 0)   8.718 us    |          }

And this patch brings two minor fixes:

- The newline after a switch-out task has disappeared
- The "|" sign just before the cpu number on task-switch has been deleted.

 0)   0.616 us    |                pick_next_task_rt();
 0)   1.457 us    |                _spin_trylock();
 0)   0.653 us    |                _spin_unlock();
 0)   0.728 us    |                _spin_trylock();
 0)   0.631 us    |                _spin_unlock();
 0)   0.729 us    |                native_load_sp0();
 0)   0.593 us    |                native_load_tls();
 ------------------------------------------
 0)    cat-2834    =>   migrati-3
 ------------------------------------------

 0)               |    finish_task_switch() {
 0)   0.841 us    |      _spin_unlock_irq();
 0)   0.616 us    |      post_schedule_rt();
 0)   3.882 us    |    }
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.c

@@ -3335,7 +3335,7 @@ static int mark_printk(const char *fmt, ...)
 	int ret;
 	va_list args;
 	va_start(args, fmt);
-	ret = trace_vprintk(0, fmt, args);
+	ret = trace_vprintk(0, -1, fmt, args);
 	va_end(args);
 	return ret;
 }
@@ -3564,9 +3564,16 @@ static __init int tracer_init_debugfs(void)
 	return 0;
 }
 
-int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
+int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
 {
-	static DEFINE_SPINLOCK(trace_buf_lock);
+	/*
+	 * Raw Spinlock because a normal spinlock would be traced here
+	 * and append an irrelevant couple spin_lock_irqsave/
+	 * spin_unlock_irqrestore traced by ftrace around this
+	 * TRACE_PRINTK trace.
+	 */
+	static raw_spinlock_t trace_buf_lock =
+				(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
 	static char trace_buf[TRACE_BUF_SIZE];
 
 	struct ring_buffer_event *event;
@@ -3587,7 +3594,8 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
 	if (unlikely(atomic_read(&data->disabled)))
 		goto out;
 
-	spin_lock_irqsave(&trace_buf_lock, flags);
+	local_irq_save(flags);
+	__raw_spin_lock(&trace_buf_lock);
 	len = vsnprintf(trace_buf, TRACE_BUF_SIZE, fmt, args);
 
 	len = min(len, TRACE_BUF_SIZE-1);
@@ -3601,13 +3609,15 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
 	tracing_generic_entry_update(&entry->ent, flags, pc);
 	entry->ent.type			= TRACE_PRINT;
 	entry->ip			= ip;
+	entry->depth			= depth;
 
 	memcpy(&entry->buf, trace_buf, len);
 	entry->buf[len] = 0;
 	ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
 
  out_unlock:
-	spin_unlock_irqrestore(&trace_buf_lock, flags);
+	__raw_spin_unlock(&trace_buf_lock);
+	local_irq_restore(flags);
 
  out:
 	preempt_enable_notrace();
@@ -3625,7 +3635,13 @@ int __ftrace_printk(unsigned long ip, const char *fmt, ...)
 		return 0;
 
 	va_start(ap, fmt);
-	ret = trace_vprintk(ip, fmt, ap);
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	ret = trace_vprintk(ip, current->curr_ret_stack, fmt, ap);
+#else
+	ret = trace_vprintk(ip, -1, fmt, ap);
+#endif
+
 	va_end(ap);
 	return ret;
 }

kernel/trace/trace.h

@@ -117,6 +117,7 @@ struct userstack_entry {
 struct print_entry {
 	struct trace_entry	ent;
 	unsigned long		ip;
+	int			depth;
 	char			buf[];
 };
 
@@ -498,7 +499,8 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip,
 extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
 				 size_t cnt);
 extern long ns2usecs(cycle_t nsec);
-extern int trace_vprintk(unsigned long ip, const char *fmt, va_list args);
+extern int
+trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args);
 
 extern unsigned long trace_flags;
 

kernel/trace/trace_functions_graph.c

@@ -173,7 +173,7 @@ verif_pid(struct trace_seq *s, pid_t pid, int cpu)
 
  */
 	ret = trace_seq_printf(s,
-		"\n ------------------------------------------\n |");
+		" ------------------------------------------\n");
 	if (!ret)
 		TRACE_TYPE_PARTIAL_LINE;
 
@@ -477,6 +477,71 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
 	return TRACE_TYPE_HANDLED;
 }
 
+static enum print_line_t
+print_graph_comment(struct print_entry *trace, struct trace_seq *s,
+		   struct trace_entry *ent, struct trace_iterator *iter)
+{
+	int i;
+	int ret;
+
+	/* Pid */
+	if (verif_pid(s, ent->pid, iter->cpu) == TRACE_TYPE_PARTIAL_LINE)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	/* Cpu */
+	if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
+		ret = print_graph_cpu(s, iter->cpu);
+		if (ret == TRACE_TYPE_PARTIAL_LINE)
+			return TRACE_TYPE_PARTIAL_LINE;
+	}
+
+	/* Proc */
+	if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
+		ret = print_graph_proc(s, ent->pid);
+		if (ret == TRACE_TYPE_PARTIAL_LINE)
+			return TRACE_TYPE_PARTIAL_LINE;
+
+		ret = trace_seq_printf(s, " | ");
+		if (!ret)
+			return TRACE_TYPE_PARTIAL_LINE;
+	}
+
+	/* No overhead */
+	if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
+		ret = trace_seq_printf(s, "  ");
+		if (!ret)
+			return TRACE_TYPE_PARTIAL_LINE;
+	}
+
+	/* No time */
+	ret = trace_seq_printf(s, "            |  ");
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	/* Indentation */
+	if (trace->depth > 0)
+		for (i = 0; i < (trace->depth + 1) * TRACE_GRAPH_INDENT; i++) {
+			ret = trace_seq_printf(s, " ");
+			if (!ret)
+				return TRACE_TYPE_PARTIAL_LINE;
+		}
+
+	/* The comment */
+	ret = trace_seq_printf(s, "/* %s", trace->buf);
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	if (ent->flags & TRACE_FLAG_CONT)
+		trace_seq_print_cont(s, iter);
+
+	ret = trace_seq_printf(s, " */\n");
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	return TRACE_TYPE_HANDLED;
+}
+
+
 enum print_line_t
 print_graph_function(struct trace_iterator *iter)
 {
@@ -495,6 +560,11 @@ print_graph_function(struct trace_iterator *iter)
 		trace_assign_type(field, entry);
 		return print_graph_return(&field->ret, s, entry, iter->cpu);
 	}
+	case TRACE_PRINT: {
+		struct print_entry *field;
+		trace_assign_type(field, entry);
+		return print_graph_comment(field, s, entry, iter);
+	}
 	default:
 		return TRACE_TYPE_UNHANDLED;
 	}

kernel/trace/trace_mmiotrace.c

@@ -366,5 +366,5 @@ void mmio_trace_mapping(struct mmiotrace_map *map)
 
 int mmio_trace_printk(const char *fmt, va_list args)
 {
-	return trace_vprintk(0, fmt, args);
+	return trace_vprintk(0, -1, fmt, args);
 }