From: Tom Zanussi <zanu...@kernel.org>
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/1567628224.13841.4.ca...@kernel.org
Link:
http://lore.kernel.org/linux-trace-devel/20200625100516.365338-3-tz.stoya...@gmail.com
Signed-off-by: Tom Zanussi <zanu...@kernel.org>
[ Ported from trace-cmd.git ]
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoya...@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org>
---
tools/lib/traceevent/kbuffer-parse.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/tools/lib/traceevent/kbuffer-parse.c
b/tools/lib/traceevent/kbuffer-parse.c
index 583db99aee94..f1640d651c8a 100644
--- a/tools/lib/traceevent/kbuffer-parse.c
+++ b/tools/lib/traceevent/kbuffer-parse.c
@@ -361,6 +361,7 @@ 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;
@@ -369,10 +370,6 @@ 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;
@@ -397,7 +394,11 @@ 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;
@@ -454,7 +455,9 @@ 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;
}
--
2.26.2
