rtems-record-lttng: Corrupted timestamps after translating to CTF

Sebastian Huber sebastian.huber at embedded-brains.de
Fri Mar 5 16:45:38 UTC 2021

On 05/03/2021 16:11, Jan.Sommer at dlr.de wrote:

> Some of the resulting CTF events have a very large timestamp. This only occurs for events of which are created by CPUs other than CPU0, but not all of them.
> I ran rtems-record-lttng in gdb and could track it to record-client.c:176 (https://git.rtems.org/rtems-tools/tree/trace/record/record-client.c#n176).
> There the (delta * ctx->to_bt_scaler ) causes an overflow and sets per_cpu->uptime.bt to a very large negative number which then later becomes a very large (positive) timestamp.
> I have some trouble figuring out what is going wrong here. The timestamps which are read from the rtems record events looks quite reasonable to me.
> The to_bt_scaler is quite a large value and I don't fully get what it scales. Does someone have some hints?
It could be related to ring buffer overflows. Do you get 
RTEMS_RECORD_PER_CPU_OVERFLOW items? There could be also some bugs in 
record-client.c. More unit tests for it would be helpful.

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