LTTng » LTTng-tools

The lttng create command's --subbuf-size, --tracefile-size and --num-subbuf options have a rounding problem.

If you give any of them an argument in the range 2^63 < size < 2^64, the command will "round it up" to 1. The size argument should be rejected instead (for the right reasons).

$ lttng create silly
Session silly created.
Traces will be written in /home/username/lttng-traces/silly-20130924-160335
$ lttng enable-channel -u ch1 --subbuf-size 0x8000000000000001
Warning: The subbuf size (9223372036854775809) is rounded to the next power of 2 (1)
Error: Channel ch1: Invalid parameter (session silly)
Warning: Some command(s) went wrong
$ lttng enable-channel -u ch1 --tracefile-size 0x8000000000000001
UST channel ch1 enabled for session silly
$ lttng enable-channel -u ch2 --num-subbuf 0x8000000000000001
Warning: The number of subbuffers (9223372036854775809) is rounded to the next power of 2 (1)
UST channel ch2 enabled for session silly
$ lttng list silly
Tracing session silly: [inactive]
    Trace path: /home/username/lttng-traces/silly-20130924-160335

=== Domain: UST global ===

Buffer type: per UID

Channels:
-------------
- ch2: [enabled]

    Attributes:
      overwrite mode: 0
      subbufers size: 131072
      number of subbufers: 1
[...]

I'm giving this bug low priority because it is so unlikely to be triggerred.