[patch 1/7] ftrace: fix task state printout

[Thomas Gleixner]

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@xxxxxxxxxxxxx>
---
 kernel/trace/trace.c |   40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

Index: linux-2.6.24/kernel/trace/trace.c
===================================================================
--- linux-2.6.24.orig/kernel/trace/trace.c
+++ linux-2.6.24/kernel/trace/trace.c
@@ -1626,6 +1626,13 @@ 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] : '?';
+}
+
 extern unsigned long sys_call_table[NR_syscalls];
 
 #if defined(CONFIG_COMPAT) && defined(CONFIG_X86)
@@ -1654,7 +1661,6 @@ print_lat_fmt(struct trace_iterator *ite
 	char *comm;
 	int S, T;
 	int i;
-	unsigned state;
 
 	if (!next_entry)
 		next_entry = entry;
@@ -1685,11 +1691,8 @@ print_lat_fmt(struct trace_iterator *ite
 		break;
 	case TRACE_CTX:
 	case TRACE_WAKE:
-		T = entry->ctx.next_state < sizeof(state_to_char) ?
-			state_to_char[entry->ctx.next_state] : 'X';
-
-		state = entry->ctx.prev_state ? __ffs(entry->ctx.prev_state) + 1 : 0;
-		S = state < sizeof(state_to_char) - 1 ? state_to_char[state] : 'X';
+		T = task_state_char(entry->ctx.next_state);
+		S = task_state_char(entry->ctx.prev_state);
 		comm = trace_find_cmdline(entry->ctx.next_pid);
 		trace_seq_printf(s, " %5d:%3d:%c %s %5d:%3d:%c %s\n",
 				 entry->ctx.prev_pid,
@@ -1862,10 +1865,8 @@ static int print_trace_fmt(struct trace_
 		break;
 	case TRACE_CTX:
 	case TRACE_WAKE:
-		S = entry->ctx.prev_state < sizeof(state_to_char) ?
-			state_to_char[entry->ctx.prev_state] : 'X';
-		T = entry->ctx.next_state < sizeof(state_to_char) ?
-			state_to_char[entry->ctx.next_state] : 'X';
+		T = task_state_char(entry->ctx.next_state);
+		S = task_state_char(entry->ctx.prev_state);
 		ret = trace_seq_printf(s, " %5d:%3d:%c %s %5d:%3d:%c\n",
 				       entry->ctx.prev_pid,
 				       entry->ctx.prev_prio,
@@ -2012,12 +2013,10 @@ static int print_raw_fmt(struct trace_it
 		break;
 	case TRACE_CTX:
 	case TRACE_WAKE:
-		S = entry->ctx.prev_state < sizeof(state_to_char) ?
-			state_to_char[entry->ctx.prev_state] : 'X';
-		T = entry->ctx.next_state < sizeof(state_to_char) ?
-			state_to_char[entry->ctx.next_state] : 'X';
-		if (entry->type == TRACE_WAKE)
-			S = '+';
+		T = task_state_char(entry->ctx.next_state);
+		S = entry->type == TRACE_WAKE ? '+' :
+			task_state_char(entry->ctx.prev_state);
+
 		ret = trace_seq_printf(s, "%d %d %c %d %d %c\n",
 				       entry->ctx.prev_pid,
 				       entry->ctx.prev_prio,
@@ -2073,12 +2072,9 @@ static int print_hex_fmt(struct trace_it
 		break;
 	case TRACE_CTX:
 	case TRACE_WAKE:
-		S = entry->ctx.prev_state < sizeof(state_to_char) ?
-			state_to_char[entry->ctx.prev_state] : 'X';
-		T = entry->ctx.next_state < sizeof(state_to_char) ?
-			state_to_char[entry->ctx.next_state] : 'X';
-		if (entry->type == TRACE_WAKE)
-			S = '+';
+		T = task_state_char(entry->ctx.next_state);
+		S = entry->type == TRACE_WAKE ? '+' :
+			task_state_char(entry->ctx.prev_state);
 		SEQ_PUT_HEX_FIELD_RET(s, entry->ctx.prev_pid);
 		SEQ_PUT_HEX_FIELD_RET(s, entry->ctx.prev_prio);
 		SEQ_PUT_HEX_FIELD_RET(s, S);

-- 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/