On Wed, Jan 21, 2015 at 5:03 PM, Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > AFAIK a trigger can be fired before allocating a ring buffer if it > doesn't use the event record (i.e. has filter) or ->post_trigger bit > set (stacktrace). Please see ftrace_trigger_soft_disabled(). yes, but such trigger has no arguments, so I would have to hack ftrace_trigger_soft_disabled() to pass 'ctx' further down and through all pointer dereferences and list walking. Also there is no return value, so I have to add it as well similar to post-triggers. that's quite a bit of overhead that I would like to avoid. Actually now I'm thinking to move condition if (ftrace_file->flags & TRACE_EVENT_FL_BPF) before ftrace_trigger_soft_disabled() check. So programs always run first and if they return non-zero then all standard processing will follow. May be return value from the program can influence triggers. That will nicely replace bpf_dump_stack()...the program will return ETT_STACKTRACE constant to trigger dump. > This also makes it keeping events in the soft-disabled state. I was never able to figure out the use case for soft-disabled state. Probably historical before static_key was done. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
