The struct event_command has a callback function called get_trigger_ops(). This callback returns the "trigger_ops" to use for the trigger. These ops define the trigger function, how to init the trigger, how to print the trigger and how to free it.
The only reason there's a callback function to get these ops is because some triggers have two types of operations. One is an "always on" operation, and the other is a "count down" operation. If a user passes in a parameter to say how many times the trigger should execute. For example: echo stacktrace:5 > events/kmem/kmem_cache_alloc/trigger It will trigger the stacktrace for the first 5 times the kmem_cache_alloc event is hit. Instead of having two different trigger_ops since the only difference between them is the tigger itself (the print, init and free functions are all the same), just use a single ops that the event_command points to and add a function field to the trigger_ops to have a count_func. When a trigger is added to an event, if there's a count attached to it and the trigger ops has the count_func field, the data allocated to represent this trigger will have a new flag set called COUNT. Then when the trigger executes, it will check if the COUNT data flag is set, and if so, it will call the ops count_func(). If that returns false, it returns without executing the trigger. After making the struct event_trigger_ops be mapped one to one with the struct event_command, merge the former into the latter. Changes since v1: https://lore.kernel.org/linux-trace-kernel/[email protected] - Removed duplicate declaration of trigger_hist_cmd (Tom Zanussi) Steven Rostedt (2): tracing: Remove get_trigger_ops() and add count_func() from trigger ops tracing: Merge struct event_trigger_ops into struct event_command ---- kernel/trace/trace.h | 124 ++++++------- kernel/trace/trace_eprobe.c | 19 +- kernel/trace/trace_events_hist.c | 143 +++++---------- kernel/trace/trace_events_trigger.c | 344 +++++++++++++----------------------- 4 files changed, 230 insertions(+), 400 deletions(-)
