[lttng-dev] Odd behaviour of lttng 2.0 kernel event listing

[Thibault, Daniel]

   When the lttng-sessiond daemon is first spawned to process a 'list -k' command, some of the kernel events are given as anonymous.  Repeating the request a second time obtains the kernel event names correctly.  This is repeatable, in the sense that it always occurs and the anonymised kernel events are always the same ones.  Clearly, something is amiss.

   If the lttng-sessiond daemon is spawned to process some other command first (e.g. 'sudo lttng list -h'), a later 'list -k' command also lists the kernel event names correctly.  Could the daemon be answering the request before it has finished initialising its modules?  Or maybe the problem is with the initialisation of individual modules?

   Here is a sample session:

$ sudo lttng list -k
Spawning a session daemon
Kernel events:
-------------
      sched_kthread_stop (type: tracepoint)
      sched_kthread_stop_ret (type: tracepoint)
      sched_wakeup (type: tracepoint)
      sched_wakeup_new (type: tracepoint)
      sched_switch (type: tracepoint)
      sched_migrate_task (type: tracepoint)
      sched_process_free (type: tracepoint)
      sched_process_exit (type: tracepoint)
      sched_wait_task (type: tracepoint)
      sched_process_wait (type: tracepoint)
      sched_process_fork (type: tracepoint)
      sched_stat_wait (type: tracepoint)
      sched_stat_sleep (type: tracepoint)
      sched_stat_iowait (type: tracepoint)
      sched_stat_runtime (type: tracepoint)
      sched_pi_setprio (type: tracepoint)
      kvm_userspace_exit (type: tracepoint)
      kvm_set_irq (type: tracepoint)
      kvm_ioapic_set_irq (type: tracepoint)
      kvm_msi_set_irq (type: tracepoint)
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
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       (type: tracepoint) [disabled]
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       (type: tracepoint) [disabled]
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       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]
       (type: tracepoint) [disabled]

$ sudo lttng list -k
Kernel events:
-------------
      sched_kthread_stop (type: tracepoint)
      sched_kthread_stop_ret (type: tracepoint)
      sched_wakeup (type: tracepoint)
      sched_wakeup_new (type: tracepoint)
      sched_switch (type: tracepoint)
      sched_migrate_task (type: tracepoint)
      sched_process_free (type: tracepoint)
      sched_process_exit (type: tracepoint)
      sched_wait_task (type: tracepoint)
      sched_process_wait (type: tracepoint)
      sched_process_fork (type: tracepoint)
      sched_stat_wait (type: tracepoint)
      sched_stat_sleep (type: tracepoint)
      sched_stat_iowait (type: tracepoint)
      sched_stat_runtime (type: tracepoint)
      sched_pi_setprio (type: tracepoint)
      kvm_userspace_exit (type: tracepoint)
      kvm_set_irq (type: tracepoint)
      kvm_ioapic_set_irq (type: tracepoint)
      kvm_msi_set_irq (type: tracepoint)
      kvm_ack_irq (type: tracepoint)
      kvm_mmio (type: tracepoint)
      kvm_fpu (type: tracepoint)
      kvm_age_page (type: tracepoint)
      kvm_try_async_get_page (type: tracepoint)
      kvm_async_pf_doublefault (type: tracepoint)
      kvm_async_pf_not_present (type: tracepoint)
      kvm_async_pf_ready (type: tracepoint)
      kvm_async_pf_completed (type: tracepoint)
      irq_handler_entry (type: tracepoint)
      irq_handler_exit (type: tracepoint)
      softirq_entry (type: tracepoint)
      softirq_exit (type: tracepoint)
      softirq_raise (type: tracepoint)
      block_rq_abort (type: tracepoint)
      block_rq_requeue (type: tracepoint)
      block_rq_complete (type: tracepoint)
      block_rq_insert (type: tracepoint)
      block_rq_issue (type: tracepoint)
      block_bio_bounce (type: tracepoint)
      block_bio_complete (type: tracepoint)
      block_bio_backmerge (type: tracepoint)
      block_bio_frontmerge (type: tracepoint)
      block_bio_queue (type: tracepoint)
      block_getrq (type: tracepoint)
      block_sleeprq (type: tracepoint)
      block_plug (type: tracepoint)
      block_unplug (type: tracepoint)
      block_split (type: tracepoint)
      block_bio_remap (type: tracepoint)
      block_rq_remap (type: tracepoint)

   I am using Ubuntu 10.10 with 2.6.38 kernel and the following lttng 2.0 packages:
(git.lttng.org)
liburcu	userspace-rcu-0.6.7+-fe0707a
lttng-ust	lttng-ust-1.9.4+-eeee05f
lttng-tools	lttng-tools-2.0-pre16+-9beed4c
lttng-modules	lttng-modules-2.0-pre11-4d3e89e
(git.efficios.com)
babeltrace	babeltrace-0.7+-6f3077a

   Note that lttng-tools-2.0-pre16+-9beed4c is not the latest (2012-01-13 21:18); I had to use it because earlier and later versions both fail to compile:

lttng-tools-2.0-pre16-032b4c3 (2011-12-23 16:19):
   ust-app.c: In function 'create_ust_channel'
   ust-app.c:618: error: 'struct lttng_ust_channel' has no member named 'shm_fd'
   ust-app.c:619: error: 'struct lttng_ust_channel' has no member named 'wait_fd'
   ust-app.c:620: error: 'struct lttng_ust_channel' has no member named 'memory_map_size'

lttng-tools-2.0-pre16+-8dd3235 (2012-01-16 18:12):
   No rule to make target `test_ust_data_trace.o'...

Daniel U. Thibault
R & D pour la défense Canada - Valcartier (RDDC Valcartier) / Defence R&D Canada - Valcartier (DRDC Valcartier)
Système de systèmes (SdS) / System of Systems (SoS)
Solutions informatiques et expérimentations (SIE) / Computing Solutions and Experimentations (CSE)
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Gouvernement du Canada / Government of Canada
<http://www.valcartier.drdc-rddc.gc.ca/>