From d1bb1088e2965df0d61785e37ccd4f6bafb0b677 Mon Sep 17 00:00:00 2001
From: Ruidong Tian <[email protected]>
Date: Fri, 13 Dec 2024 10:51:33 +0800
Subject: [PATCH 73/85] tools lib traceevent: Add proper
 KBUFFER_TYPE_TIME_STAMP handling

Kernel commit dc4e2801d400 (ring-buffer: Redefine the unimplemented
RINGBUF_TYPE_TIME_STAMP) changed the way the ring buffer timestamps work
- after that commit the previously unimplemented RINGBUF_TYPE_TIME_STAMP
type causes the time delta to be used as a timestamp rather than a delta
to be added to the timestamp.

The trace-cmd code didn't get updated to handle this, so misinterprets
the event data for this case, which causes a cascade of errors,
including trace-report not being able to identify synthetic (or any
other) events generated by the histogram code (which uses TIME_STAMP
mode).  For example, the following triggers along with the trace-cmd
shown cause an UNKNOWN_EVENT error and trace-cmd report crash:

  # echo 'wakeup_latency  u64 lat pid_t pid char comm[16]' > /sys/kernel/debug/tracing/synthetic_events

  # echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
  # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_wakeup).trace(wakeup_latency,$wakeup_lat,next_pid,next_comm) if next_comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # echo 'hist:keys=comm,pid,lat:wakeup_lat=lat:sort=lat' > /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger

  # trace-cmd record -e wakeup_latency -e sched_wakeup -f comm==\"ping\" ping localhost -c 5

  # trace-cmd report
  CPU 0 is empty
  CPU 1 is empty
  CPU 2 is empty
  CPU 3 is empty
  CPU 5 is empty
  CPU 6 is empty
  CPU 7 is empty
  cpus=8
    ug! no event found for type 0
  [UNKNOWN TYPE 0]
    ug! no event found for type 11520
  Segmentation fault (core dumped)

After this patch we get the correct interpretation and the events are
shown properly:

  # trace-cmd report
  CPU 0 is empty
  CPU 1 is empty
  CPU 2 is empty
  CPU 3 is empty
  CPU 5 is empty
  CPU 6 is empty
  CPU 7 is empty
  cpus=8
          <idle>-0     [004] 23284.341392: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23284.341464: wakeup_latency:       lat=58, pid=12031, comm=ping
          <idle>-0     [004] 23285.365303: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23285.365382: wakeup_latency:       lat=64, pid=12031, comm=ping
          <idle>-0     [004] 23286.389290: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23286.389378: wakeup_latency:       lat=72, pid=12031, comm=ping
          <idle>-0     [004] 23287.413213: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23287.413291: wakeup_latency:       lat=64, pid=12031, comm=ping

Link: http://lkml.kernel.org/r/[email protected]
Link: http://lore.kernel.org/linux-trace-devel/[email protected]

Signed-off-by: Tom Zanussi <[email protected]>
[ Ported from trace-cmd.git ]
Cc: Andrew Morton <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: [email protected]
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Tzvetomir Stoyanov (VMware) <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
 libtrace/kbuffer-parse.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/libtrace/kbuffer-parse.c b/libtrace/kbuffer-parse.c
index 01d4d4f..074f619 100644
--- a/libtrace/kbuffer-parse.c
+++ b/libtrace/kbuffer-parse.c
@@ -378,6 +378,7 @@ translate_data(struct kbuffer *kbuf, void *data, void **rptr,
 		break;
 
 	case KBUFFER_TYPE_TIME_EXTEND:
+	case KBUFFER_TYPE_TIME_STAMP:
 		extend = read_4(kbuf, data);
 		data += 4;
 		extend <<= TS_SHIFT;
@@ -386,10 +387,6 @@ translate_data(struct kbuffer *kbuf, void *data, void **rptr,
 		*length = 0;
 		break;
 
-	case KBUFFER_TYPE_TIME_STAMP:
-		data += 12;
-		*length = 0;
-		break;
 	case 0:
 		*length = read_4(kbuf, data) - 4;
 		*length = (*length + 3) & ~3;
@@ -414,7 +411,11 @@ static unsigned int update_pointers(struct kbuffer *kbuf)
 
 	type_len = translate_data(kbuf, ptr, &ptr, &delta, &length);
 
-	kbuf->timestamp += delta;
+	if (type_len == KBUFFER_TYPE_TIME_STAMP)
+		kbuf->timestamp = delta;
+	else
+		kbuf->timestamp += delta;
+
 	kbuf->index = calc_index(kbuf, ptr);
 	kbuf->next = kbuf->index + length;
 
@@ -471,7 +472,9 @@ static int __next_event(struct kbuffer *kbuf)
 		if (kbuf->next >= kbuf->size)
 			return -1;
 		type = update_pointers(kbuf);
-	} while (type == KBUFFER_TYPE_TIME_EXTEND || type == KBUFFER_TYPE_PADDING);
+	} while (type == KBUFFER_TYPE_TIME_EXTEND ||
+		 type == KBUFFER_TYPE_TIME_STAMP ||
+		 type == KBUFFER_TYPE_PADDING);
 
 	return 0;
 }
-- 
2.33.1