Re: [PATCH v4 2/2] tracing: Drain deferred trigger frees if kthread creation fails

[Wesley Atwell]

Yes,

This kernel command line reliably reaches trigger_data_free() during boot:

trace_event=sched:sched_switch
trace_trigger=sched_switch.traceon,sched_switch.traceon

On an unpatched tree, that crashes during early boot before userspace.
The call trace goes through:

trigger_data_free()
__kthread_create_on_node()
try_to_wake_up()

The stack also shows the boot-time trigger registration path:

event_trigger_parse()
trigger_process_regex()
__trace_early_add_events()

With v4 applied, the same command line boots successfully. The guest log shows:

Failed to register trigger 'traceon' on event sched_switch

And /sys/kernel/tracing/events/sched/sched_switch/trigger contains:

traceon:unlimited

I also verified patch 1 with repeated trace_trigger= parameters:
before the patch, only the last parameter was preserved; after the
patch, both triggers were installed.

Thanks,
Wesley Atwell