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Date:	Mon, 29 Sep 2008 20:18:34 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	mingo@...e.hu, pq@....fi, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH V2 -tip 1/4] Tracing/ftrace: Change the type of the print_line
 callback

We need a kind of disambiguation when a print_line callback
returns 0.

_There is not enough space to print all the entry. 
 Please flush the seq and retry.
_I can't handle this type of entry

This patch changes the type of this callback for better information.

Also some changes have been made in this V2.

_ Only relay to default functions after the print_line callback fails.
_ This patch doesn't fix the issue with the broken pipe (see patch 2/4 for that)

Some things are still in discussion:

_ Find better names for the enum print_line_t values
_ Change the type of print_trace_line into boolean.

Patches to change that can be sent later.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 kernel/trace/trace.c |   77 ++++++++++++++++++++++++++-----------------------
 kernel/trace/trace.h |   10 ++++++-
 2 files changed, 50 insertions(+), 37 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6ada059..61f33da 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1510,7 +1510,7 @@ void trace_seq_print_cont(struct trace_seq *s, struct trace_iterator *iter)
 		trace_seq_putc(s, '\n');
 }
 
-static int
+static enum print_line_t
 print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
 {
 	struct trace_seq *s = &iter->seq;
@@ -1530,7 +1530,7 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
 		next_entry = entry;
 
 	if (entry->type == TRACE_CONT)
-		return 1;
+		return TRACE_TYPE_HANDLED;
 
 	rel_usecs = ns2usecs(next_entry->field.t - entry->field.t);
 	abs_usecs = ns2usecs(entry->field.t - iter->tr->time_start);
@@ -1601,10 +1601,10 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
 	default:
 		trace_seq_printf(s, "Unknown type %d\n", entry->type);
 	}
-	return 1;
+	return TRACE_TYPE_HANDLED;
 }
 
-static int print_trace_fmt(struct trace_iterator *iter)
+static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
 {
 	struct trace_seq *s = &iter->seq;
 	unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
@@ -1621,7 +1621,7 @@ static int print_trace_fmt(struct trace_iterator *iter)
 	entry = iter->ent;
 
 	if (entry->type == TRACE_CONT)
-		return 1;
+		return TRACE_TYPE_HANDLED;
 
 	field = &entry->field;
 
@@ -1633,24 +1633,24 @@ static int print_trace_fmt(struct trace_iterator *iter)
 
 	ret = trace_seq_printf(s, "%16s-%-5d ", comm, field->pid);
 	if (!ret)
-		return 0;
+		return TRACE_TYPE_PARTIAL_LINE;
 	ret = trace_seq_printf(s, "[%03d] ", iter->cpu);
 	if (!ret)
-		return 0;
+		return TRACE_TYPE_PARTIAL_LINE;
 	ret = trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
 	if (!ret)
-		return 0;
+		return TRACE_TYPE_PARTIAL_LINE;
 
 	switch (entry->type) {
 	case TRACE_FN:
 		ret = seq_print_ip_sym(s, field->fn.ip, sym_flags);
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		if ((sym_flags & TRACE_ITER_PRINT_PARENT) &&
 						field->fn.parent_ip) {
 			ret = trace_seq_printf(s, " <-");
 			if (!ret)
-				return 0;
+				return TRACE_TYPE_PARTIAL_LINE;
 			if (kretprobed(field->fn.parent_ip))
 				ret = trace_seq_puts(s, KRETPROBE_MSG);
 			else
@@ -1658,11 +1658,11 @@ static int print_trace_fmt(struct trace_iterator *iter)
 						       field->fn.parent_ip,
 						       sym_flags);
 			if (!ret)
-				return 0;
+				return TRACE_TYPE_PARTIAL_LINE;
 		}
 		ret = trace_seq_printf(s, "\n");
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		break;
 	case TRACE_CTX:
 	case TRACE_WAKE:
@@ -1680,7 +1680,7 @@ static int print_trace_fmt(struct trace_iterator *iter)
 				       field->ctx.next_prio,
 				       T);
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		break;
 	case TRACE_SPECIAL:
 		ret = trace_seq_printf(s, "# %ld %ld %ld\n",
@@ -1688,23 +1688,23 @@ static int print_trace_fmt(struct trace_iterator *iter)
 				 field->special.arg2,
 				 field->special.arg3);
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		break;
 	case TRACE_STACK:
 		for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
 			if (i) {
 				ret = trace_seq_puts(s, " <= ");
 				if (!ret)
-					return 0;
+					return TRACE_TYPE_PARTIAL_LINE;
 			}
 			ret = seq_print_ip_sym(s, field->stack.caller[i],
 					       sym_flags);
 			if (!ret)
-				return 0;
+				return TRACE_TYPE_PARTIAL_LINE;
 		}
 		ret = trace_seq_puts(s, "\n");
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		break;
 	case TRACE_PRINT:
 		seq_print_ip_sym(s, field->print.ip, sym_flags);
@@ -1713,10 +1713,10 @@ static int print_trace_fmt(struct trace_iterator *iter)
 			trace_seq_print_cont(s, iter);
 		break;
 	}
-	return 1;
+	return TRACE_TYPE_HANDLED;
 }
 
-static int print_raw_fmt(struct trace_iterator *iter)
+static enum print_line_t print_raw_fmt(struct trace_iterator *iter)
 {
 	struct trace_seq *s = &iter->seq;
 	struct trace_entry *entry;
@@ -1727,14 +1727,14 @@ static int print_raw_fmt(struct trace_iterator *iter)
 	entry = iter->ent;
 
 	if (entry->type == TRACE_CONT)
-		return 1;
+		return TRACE_TYPE_HANDLED;
 
 	field = &entry->field;
 
 	ret = trace_seq_printf(s, "%d %d %llu ",
 		field->pid, iter->cpu, field->t);
 	if (!ret)
-		return 0;
+		return TRACE_TYPE_PARTIAL_LINE;
 
 	switch (entry->type) {
 	case TRACE_FN:
@@ -1742,7 +1742,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
 					field->fn.ip,
 					field->fn.parent_ip);
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		break;
 	case TRACE_CTX:
 	case TRACE_WAKE:
@@ -1761,7 +1761,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
 				       field->ctx.next_prio,
 				       T);
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		break;
 	case TRACE_SPECIAL:
 	case TRACE_STACK:
@@ -1770,7 +1770,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
 				 field->special.arg2,
 				 field->special.arg3);
 		if (!ret)
-			return 0;
+			return TRACE_TYPE_PARTIAL_LINE;
 		break;
 	case TRACE_PRINT:
 		trace_seq_printf(s, "# %lx %s",
@@ -1779,7 +1779,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
 			trace_seq_print_cont(s, iter);
 		break;
 	}
-	return 1;
+	return TRACE_TYPE_HANDLED;
 }
 
 #define SEQ_PUT_FIELD_RET(s, x)				\
@@ -1794,7 +1794,7 @@ do {							\
 		return 0;				\
 } while (0)
 
-static int print_hex_fmt(struct trace_iterator *iter)
+static enum print_line_t print_hex_fmt(struct trace_iterator *iter)
 {
 	struct trace_seq *s = &iter->seq;
 	unsigned char newline = '\n';
@@ -1805,7 +1805,7 @@ static int print_hex_fmt(struct trace_iterator *iter)
 	entry = iter->ent;
 
 	if (entry->type == TRACE_CONT)
-		return 1;
+		return TRACE_TYPE_HANDLED;
 
 	field = &entry->field;
 
@@ -1843,10 +1843,10 @@ static int print_hex_fmt(struct trace_iterator *iter)
 	}
 	SEQ_PUT_FIELD_RET(s, newline);
 
-	return 1;
+	return TRACE_TYPE_HANDLED;
 }
 
-static int print_bin_fmt(struct trace_iterator *iter)
+static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
 {
 	struct trace_seq *s = &iter->seq;
 	struct trace_entry *entry;
@@ -1855,7 +1855,7 @@ static int print_bin_fmt(struct trace_iterator *iter)
 	entry = iter->ent;
 
 	if (entry->type == TRACE_CONT)
-		return 1;
+		return TRACE_TYPE_HANDLED;
 
 	field = &entry->field;
 
@@ -1883,7 +1883,7 @@ static int print_bin_fmt(struct trace_iterator *iter)
 		SEQ_PUT_FIELD_RET(s, field->special.arg3);
 		break;
 	}
-	return 1;
+	return TRACE_TYPE_HANDLED;
 }
 
 static int trace_empty(struct trace_iterator *iter)
@@ -1902,10 +1902,15 @@ static int trace_empty(struct trace_iterator *iter)
 	return 1;
 }
 
-static int print_trace_line(struct trace_iterator *iter)
+static enum print_line_t print_trace_line(struct trace_iterator *iter)
 {
-	if (iter->trace && iter->trace->print_line)
-		return iter->trace->print_line(iter);
+	enum print_line_t ret;
+
+	if (iter->trace && iter->trace->print_line) {
+		ret = iter->trace->print_line(iter);
+		if (ret != TRACE_TYPE_UNHANDLED)
+			return ret;
+	}
 
 	if (trace_flags & TRACE_ITER_BIN)
 		return print_bin_fmt(iter);
@@ -2715,11 +2720,11 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 	}
 
 	while (find_next_entry_inc(iter) != NULL) {
-		int ret;
+		enum print_line_t ret;
 		int len = iter->seq.len;
 
 		ret = print_trace_line(iter);
-		if (!ret) {
+		if (ret == TRACE_TYPE_PARTIAL_LINE) {
 			/* don't print partial lines */
 			iter->seq.len = len;
 			break;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index b28bf88..73cd7c5 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -180,6 +180,14 @@ struct trace_array {
 	struct trace_array_cpu	*data[NR_CPUS];
 };
 
+
+/* Return values for print_line callback */
+enum print_line_t {
+	TRACE_TYPE_PARTIAL_LINE	= 0,	/* Retry after flushing the seq */
+	TRACE_TYPE_HANDLED	= 1,
+	TRACE_TYPE_UNHANDLED	= 2	/* Relay to other output functions */
+};
+
 /*
  * A specific tracer, represented by methods that operate on a trace array:
  */
@@ -200,7 +208,7 @@ struct tracer {
 	int			(*selftest)(struct tracer *trace,
 					    struct trace_array *tr);
 #endif
-	int			(*print_line)(struct trace_iterator *iter);
+	enum print_line_t	(*print_line)(struct trace_iterator *iter);
 	struct tracer		*next;
 	int			print_max;
 };
--
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