linux-kernel - [PATCH 1/9] tracing: Dont print an extra separator of flags

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Date:	Wed, 22 Feb 2012 09:40:37 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Andrew Vagin <avagin@...nvz.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: [PATCH 1/9] tracing: Dont print an extra separator of flags

From: Andrey Vagin <avagin@...nvz.org>

If __print_flags() is used after another __print_*() function, the
temp seq_file buffer will not be empty on entry, and the delimiter will
be printed even though there's just one field. We get something like:

	|S

instead of just:

	S

This is because the length of the temp seq buffer is used to determine
if the delimiter is printed or not. But this algorithm fails when
the seq buffer is not empty on entry, and the delimiter will be printed
because it thinks that a previous field was already printed.

Link: http://lkml.kernel.org/r/1329650167-480655-1-git-send-email-avagin@openvz.org

Signed-off-by: Andrew Vagin <avagin@...nvz.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/trace/trace_output.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 0d6ff355..3efd718 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -300,7 +300,7 @@ ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
 	unsigned long mask;
 	const char *str;
 	const char *ret = p->buffer + p->len;
-	int i;
+	int i, first = 1;
 
 	for (i = 0;  flag_array[i].name && flags; i++) {
 
@@ -310,8 +310,10 @@ ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
 
 		str = flag_array[i].name;
 		flags &= ~mask;
-		if (p->len && delim)
+		if (!first && delim)
 			trace_seq_puts(p, delim);
+		else
+			first = 0;
 		trace_seq_puts(p, str);
 	}
 
-- 
1.7.8.3



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