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authorDaniel Bristot de Oliveira <bristot@redhat.com>2017-01-03 12:42:42 +0100
committerArnaldo Carvalho de Melo <acme@redhat.com>2017-01-03 16:11:12 -0300
commit074859184d770824f4437dca716bdeb625ae8b1c (patch)
tree92058008461cf11062e6897a331fff18b67005fd /tools
parent60437ac02f398e0ee0927748d4798dd5534ac90d (diff)
tools lib traceevent: Fix prev/next_prio for deadline tasks
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@redhat.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/866ef75bcebf670ae91c6a96daa63597ba981f0d.1483443552.git.bristot@redhat.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/lib/traceevent/plugin_sched_switch.c4
1 files 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;
}