Re: [RFC PATCH v2 3/3] libtraceevent: use the new prev_state_char instead in tracepoint sched_switch

Roger that!

Thanks,
Ze

On Mon, Jul 31, 2023 at 11:40 PM Steven Rostedt [off-list ref] wrote:

On Wed, 26 Jul 2023 20:16:18 +0800
Ze Gao [off-list ref] wrote:

quoted

Since the sched_switch tracepoint introduces a new variable to
report sched-out task state in symbolic char, we switch to use
that instead to spare from knowing internal implementations
in kernel.

This needs to be changed to check if the "prev_state_char" field exists,
and if not, then it must use the old method. Same for perf. The tools must
work with older kernels.

-- Steve

quoted

Signed-off-by: Ze Gao <redacted>
---
 plugins/plugin_sched_switch.c | 29 ++++-------------------------
 1 file changed, 4 insertions(+), 25 deletions(-)

diff --git a/plugins/plugin_sched_switch.c b/plugins/plugin_sched_switch.c
index 8752cae..5dbdc28 100644
--- a/plugins/plugin_sched_switch.c
+++ b/plugins/plugin_sched_switch.c

@@ -9,27 +9,6 @@
 #include "event-parse.h"
 #include "trace-seq.h"

-static void write_state(struct trace_seq *s, int val)
-{
-     const char states[] = "SDTtZXxW";
-     int found = 0;
-     int i;
-
-     for (i = 0; i < (sizeof(states) - 1); i++) {
-             if (!(val & (1 << i)))
-                     continue;
-
-             if (found)
-                     trace_seq_putc(s, '|');
-
-             found = 1;
-             trace_seq_putc(s, states[i]);
-     }
-
-     if (!found)
-             trace_seq_putc(s, 'R');
-}
-
 static void write_and_save_comm(struct tep_format_field *field,
                              struct tep_record *record,
                              struct trace_seq *s, int pid)

@@ -97,10 +76,10 @@ static int sched_switch_handler(struct trace_seq *s,
      trace_seq_printf(s, "%lld ", val);

      if (tep_get_field_val(s, event, "prev_prio", record, &val, 1) ==

0)
-             trace_seq_printf(s, "[%d] ", (int) val);
+             trace_seq_printf(s, "[%d] ", (short) val);

-     if (tep_get_field_val(s,  event, "prev_state", record, &val, 1)
== 0)
-             write_state(s, val);
+     if (tep_get_field_val(s,  event, "prev_state_char", record,
&val, 1) == 0)
+             trace_seq_putc(s, (char) val);

      trace_seq_puts(s, " ==> ");

@@ -115,7 +94,7 @@ static int sched_switch_handler(struct trace_seq *s,
      trace_seq_printf(s, "%lld", val);

      if (tep_get_field_val(s, event, "next_prio", record, &val, 1) ==

0)
-             trace_seq_printf(s, " [%d]", (int) val);
+             trace_seq_printf(s, " [%d]", (short) val);

      return 0;
 }