From: Daniel Bristot de Oliveiva <[email protected]>
Currently, the sched:sched_switch tracepoint reports deadline tasks
with priority -1. But when reading the trace via perf script I've
got the following output:
# ./d & # (d is a deadline task, see [1])
# perf record -e sched:sched_switch -a sleep 1
# perf script
...
swapper 0 [000] 2146.962441: sched:sched_switch: swapper/0:0
[120] R ==> d:2593 [4294967295]
d 2593 [000] 2146.972472: sched:sched_switch: d:2593
[4294967295] R ==> g:2590 [4294967295]
The task d reports the wrong priority [4294967295]. This happens because
the "int prio" is stored in an unsigned long long val. Although it is
set as a %lld, as int is shorter than unsigned long long,
trace_seq_printf prints it as a positive number.
The fix is just to cast the val as an int, and print it as a %d,
as in the sched:sched_switch tracepoint's "format".
The output with the fix is:
# ./d &
# perf record -e sched:sched_switch -a sleep 1
# perf script
...
swapper 0 [000] 4306.374037: sched:sched_switch: swapper/0:0
[120] R ==> d:10941 [-1]
d 10941 [000] 4306.383823: sched:sched_switch: d:10941 [-1] R
==> swapper/0:0 [120]
[1] gcc -o d d.c - from http://bristot.me/lkml/d.c
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: [email protected]
diff --git a/tools/lib/traceevent/plugin_sched_switch.c
b/tools/lib/traceevent/plugin_sched_switch.c
index f1ce600..ec30c2f 100644
--- a/tools/lib/traceevent/plugin_sched_switch.c
+++ b/tools/lib/traceevent/plugin_sched_switch.c
@@ -111,7 +111,7 @@ static int sched_switch_handler(struct trace_seq *s,
trace_seq_printf(s, "%lld ", val);
if (pevent_get_field_val(s, event, "prev_prio", record, &val, 0) == 0)
- trace_seq_printf(s, "[%lld] ", val);
+ trace_seq_printf(s, "[%d] ", (int) val);
if (pevent_get_field_val(s, event, "prev_state", record, &val, 0) == 0)
write_state(s, val);
@@ -129,7 +129,7 @@ static int sched_switch_handler(struct trace_seq *s,
trace_seq_printf(s, "%lld", val);
if (pevent_get_field_val(s, event, "next_prio", record, &val, 0) == 0)
- trace_seq_printf(s, " [%lld]", val);
+ trace_seq_printf(s, " [%d]", (int) val);
return 0;
}
--
2.9.3
