From: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
[ Upstream commit 074859184d770824f4437dca716bdeb625ae8b1c ]
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] d.c
---
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <linux/types.h>
#include <linux/sched.h>
struct sched_attr {
__u32 size, sched_policy;
__u64 sched_flags;
__s32 sched_nice;
__u32 sched_priority;
__u64 sched_runtime, sched_deadline, sched_period;
};
int sched_setattr(pid_t pid, const struct sched_attr *attr, unsigned int flags)
{
return syscall(__NR_sched_setattr, pid, attr, flags);
}
int main(void)
{
struct sched_attr attr = {
.size = sizeof(attr),
.sched_policy = SCHED_DEADLINE, /* This creates a 10ms/30ms reservation */
.sched_runtime = 10 * 1000 * 1000,
.sched_period = attr.sched_deadline = 30 * 1000 * 1000,
};
if (sched_setattr(0, &attr, 0) < 0) {
perror("sched_setattr");
return -1;
}
for(;;);
}
---
Committer notes:
Got the program from the provided URL, http://bristot.me/lkml/d.c,
trimmed it and included in the cset log above, so that we have
everything needed to test it in one place.
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/866ef75bcebf670ae91c6a96daa63597ba981f0d.1483443552.git.bristot@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
tools/lib/traceevent/plugin_sched_switch.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/lib/traceevent/plugin_sched_switch.c b/tools/lib/traceevent/plugin_sched_switch.c
index f1ce60065258..ec30c2fcbac0 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;
}
--
2.11.0