linux-kernel - trace: fix task state printout

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Date:	Wed, 17 Dec 2008 22:34:13 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	LKML <linux-kernel@...r.kernel.org>
cc:	Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>
Subject: trace: fix task state printout

Impact: tracer task state decoding is wrong, size check is buggy

The tracing code has interesting varieties of printing out task state.
Unfortunalely only one of the instances is correct as it copies the
code from sched.c:sched_show_task(). The others are plain wrong as
they treatthe bitfield as an integer offset into the character
array. Also the size check of the character array is wrong as it
includes the trailing \0.

Use a common state decoder inline which does the Right Thing.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/trace/trace.c |   39 +++++++++++++++++----------------------
 1 file changed, 17 insertions(+), 22 deletions(-)

Index: linux-2.6/kernel/trace/trace.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace.c
+++ linux-2.6/kernel/trace/trace.c
@@ -1301,6 +1301,13 @@ lat_print_timestamp(struct trace_seq *s,
 
 static const char state_to_char[] = TASK_STATE_TO_CHAR_STR;
 
+static int task_state_char(unsigned long state)
+{
+	int bit = state ? __ffs(state) + 1 : 0;
+
+	return bit < sizeof(state_to_char) - 1 ? state_to_char[bit] : '?';
+}
+
 /*
  * The message is supposed to contain an ending newline.
  * If the printing stops prematurely, try to add a newline of our own.
@@ -1395,12 +1402,8 @@ print_lat_fmt(struct trace_iterator *ite
 
 		trace_assign_type(field, entry);
 
-		T = field->next_state < sizeof(state_to_char) ?
-			state_to_char[field->next_state] : 'X';
-
-		state = field->prev_state ?
-			__ffs(field->prev_state) + 1 : 0;
-		S = state < sizeof(state_to_char) - 1 ? state_to_char[state] : 'X';
+		T = task_state_char(field->next_state);
+		S = task_state_char(field->prev_state);
 		comm = trace_find_cmdline(field->next_pid);
 		trace_seq_printf(s, " %5d:%3d:%c %s [%03d] %5d:%3d:%c %s\n",
 				 field->prev_pid,
@@ -1518,10 +1521,8 @@ static enum print_line_t print_trace_fmt
 
 		trace_assign_type(field, entry);
 
-		S = field->prev_state < sizeof(state_to_char) ?
-			state_to_char[field->prev_state] : 'X';
-		T = field->next_state < sizeof(state_to_char) ?
-			state_to_char[field->next_state] : 'X';
+		T = task_state_char(field->next_state);
+		S = task_state_char(field->prev_state);
 		ret = trace_seq_printf(s, " %5d:%3d:%c %s [%03d] %5d:%3d:%c\n",
 				       field->prev_pid,
 				       field->prev_prio,
@@ -1620,12 +1621,9 @@ static enum print_line_t print_raw_fmt(s
 
 		trace_assign_type(field, entry);
 
-		S = field->prev_state < sizeof(state_to_char) ?
-			state_to_char[field->prev_state] : 'X';
-		T = field->next_state < sizeof(state_to_char) ?
-			state_to_char[field->next_state] : 'X';
-		if (entry->type == TRACE_WAKE)
-			S = '+';
+		T = task_state_char(field->next_state);
+		S = entry->type == TRACE_WAKE ? '+' :
+			task_state_char(field->prev_state);
 		ret = trace_seq_printf(s, "%d %d %c %d %d %d %c\n",
 				       field->prev_pid,
 				       field->prev_prio,
@@ -1711,12 +1709,9 @@ static enum print_line_t print_hex_fmt(s
 
 		trace_assign_type(field, entry);
 
-		S = field->prev_state < sizeof(state_to_char) ?
-			state_to_char[field->prev_state] : 'X';
-		T = field->next_state < sizeof(state_to_char) ?
-			state_to_char[field->next_state] : 'X';
-		if (entry->type == TRACE_WAKE)
-			S = '+';
+		T = task_state_char(field->next_state);
+		S = entry->type == TRACE_WAKE ? '+' :
+			task_state_char(field->prev_state);
 		SEQ_PUT_HEX_FIELD_RET(s, field->prev_pid);
 		SEQ_PUT_HEX_FIELD_RET(s, field->prev_prio);
 		SEQ_PUT_HEX_FIELD_RET(s, S);
--
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