On 11/9/21 5:28 PM, Steven Rostedt wrote: > [ Hmm, should add Mathieu in on this discussion ] > > On Tue, 9 Nov 2021 17:13:13 -0500 > Jason Baron <jbaron@xxxxxxxxxx> wrote: > >>> What we are looking at there is to pass the dynamic debug descriptor to the >>> trace event filtering logic, where you could filter on information passed >>> to it. For example, on a specific file if a trace event is called by >>> several different files or modules. >>> >>> -- Steve >> >> Ok, Could this be done at the dynamic debug level as it can already match >> on specific files and line numbers currently? > > Not sure what you mean by that. I was just trying to say that via dynamic debug one could enable all debugs in a kernel source directory as in your example below via: # echo "file drivers/soc/qcom/* +p" > /sys/kernel/debug/dynamic_debug/control So if we are just looking for a printk here, one could just use pr_debug(). Or if we want that print to go the tracing ring buffer we have been discussing how to add that as a 'backend' for dynamic debug as well. If we want to use tracepionts, then yeah I think it's going to require adding the file, line, module data to each tracepoint site. I think this is probably done via the tracing macros and then that could be filtered on, but yes that's going to add bloat. The proposal here seems to be a mix of things - use the file control that dynamic debug already has to match on file name and then enable a tracepoint that is behind it. That seems overly complex? Thanks, -Jason > > The idea was that this would only be enabled if dynamic debug is enabled > and that the DEFINE_DYNAMIC_DEBUG_METADATA() could be used at the > tracepoint function location (trace_foo()) by the tracepoint macros. And > then if one of the callbacks registered for the tracepoint had a > "dynamic_debug" flag set, it would be passed the descriptor in as a pointer. > > And then, for example, the filtering logic of ftrace could then reference > the information of the event, if the user passed in something special. > > # echo 'DEBUG_FILE ~ "drivers/soc/qcom/*"' > events/rwmmio/rwmmio_write/filter > # echo 1 > events/rwmmio/rwmmio_write/enable > > And then only the rwmmio_write events that came from the qcom directory > would be printed. > > We would create special event fields like "DEBUG_FILE", "DEBUG_FUNC", > "DEBUG_MOD", "DEBUG_LINE", etc, that could be used if dyndebug is enabled > in the kernel. > > Of course this is going to bloat the kernel as it will create a dynamic > debug descriptor at every tracepoint location. > > -- Steve >
