On Mon, 19 Apr 2021 21:54:13 +0000 "Williams, Dan J" <[email protected]> wrote:
> [ drop Rusty, add Jessica and Emmanuel ] Probably could have kept Jessica on as she's the module maintainer. > > On Wed, 2013-08-14 at 23:32 -0400, Steven Rostedt wrote: > > On Thu, 15 Aug 2013 11:32:10 +0930 Wow, this is coming back from the dead! No thread rests in peace! > > Rusty Russell <[email protected]> wrote: > > > > > Steven Rostedt <[email protected]> writes: > > > > But the thing about this that bothers me is that there's no way > > > > to say, > > > > "Enable all tracepoints in this module on load". I would like a > > > > way to > > > > do that, but I don't know of a way to do that without modifying > > > > the > > > > module code. Have any ideas? Basically, I would love to have: > > > > > > > > insmod foo tracepoints=all > > > > > > > > or something and have all tracepoints enabled. > > > > > > "without modifying the module code"? Why? The code isn't that > > > scary, > > > and this seems useful. > > > > I'm not afraid of the code, I'm afraid of you ;-) I hear you have > > killer puppies. > > > > > > OK, then when I get some time, I may cook something up. "when I get some time" HAHAHAHAHAHAH!!!! That was what? 8 years ago! > > > > Thanks, > > > > -- Steve > > Revive an old thread... I'll say! > > Steven, did you ever end up with a solution to the "enable tracing at > module load" problem? For tracepoints, no. For function tracing, yes! > > I see some people getting admonished to use ftrace over dev_dbg() [1], > but one of the features that keeps dev_dbg() proliferating is its > generic "$mod_name.dyndbg=" module parameter support for selective > debug enabling at boot / module-load. > > It would be useful to be able to do > /sys/kernel/debug/dynamic_debug/control enabling for tracepoints, but > also module::function_name patterns for "got here" style debugging. I'd > be happy to help with this, but wanted to understand where you left > things. > > [1]: https://lore.kernel.org/linux-wireless/yhrfy3aq%[email protected]/ I don't think I did anything with trace events, I'll have to dig deeper. But today you have this: # cd /sys/kernel/tracing # rmmod bridge # echo ':mod:bridge' > set_ftrace_filter # cat set_ftrace_filter :mod:bridge # echo function > current_tracer # cat trace # tracer: function # # entries-in-buffer/entries-written: 0/0 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | # modprobe bridge # cat set_ftrace_filter br_switchdev_event [bridge] br_device_event [bridge] br_net_exit [bridge] br_boolopt_get [bridge] br_boolopt_multi_get [bridge] br_opt_toggle [bridge] br_boolopt_toggle [bridge] br_boolopt_multi_toggle [bridge] br_dev_set_multicast_list [bridge] br_get_link_ksettings [bridge] [..] # cat trace # tracer: function # # entries-in-buffer/entries-written: 10/10 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | modprobe-2364 [006] .... 12929.869510: br_init <-do_one_initcall modprobe-2364 [006] .... 12929.869513: br_fdb_init <-br_init modprobe-2364 [006] .... 12929.869522: br_device_event <-call_netdevice_register_net_notifiers modprobe-2364 [006] .... 12929.869522: br_device_event <-call_netdevice_register_net_notifiers modprobe-2364 [006] .... 12929.869522: br_device_event <-call_netdevice_register_net_notifiers modprobe-2364 [006] .... 12929.869522: br_device_event <-call_netdevice_register_net_notifiers modprobe-2364 [006] .... 12929.869523: br_device_event <-call_netdevice_register_net_notifiers modprobe-2364 [006] .... 12929.869523: br_device_event <-call_netdevice_register_net_notifiers modprobe-2364 [006] .... 12929.869524: br_netlink_init <-br_init modprobe-2364 [006] .... 12929.869524: br_mdb_init <-br_netlink_init So yes, function tracing now allows setting a filter to trace only the functions for a given module, and if that module is not yet loaded, it stores the filter until it is. To do something similar for tracepoints, I think we still need to add it as a module parameter. -- Steve
