The tracers (like function and function_graph) have options that modify how they behave or how they are shown in the trace file. As these options were created before instances (multiple buffers), the flags variable that represent these options were global for the tracer.
Now that a tracer may exist in multiple instances, having a global flags that kinda affect every instance of that tracer does not make sense. The reason it "kinda" affects them, is that the code that updates an option for an instance, only does the change for the tracer running in that instance. If a tracer is already running in another instance, it will not be affected. But because the option is saved in a global variable, if the tracer is stopped and restarted in the instance, then the option will take affect. Since each instance has its own interface to modify the options, the effect of an option should only affect the tracer for the given instance. This means that the state of the options for each tracer must be saved for each instance separately. Add a new struct tracers field in the trace_array (instance descriptor) that holds a descriptor that points to a tracer and contains its flags values. This will be used to see what tracers are available for an instance. Now when a tracer option is modified for an instance, it only affects the tracer in that instance and not semi-effects the tracers in other instances. Changes since v3: https://lore.kernel.org/linux-trace-kernel/[email protected]/ - Fix registering of command line tracers. A command line tracer is registered before the global array attaches itself to the list of instances. This keeps the tracer from attaching to the global array and that keeps the tracer from adding itself to the global array, and this means it fails to start at boot. - Also add a warning if the starting of a boot tracer fails to start. Steven Rostedt (3): tracing: Have tracer option be instance specific tracing: Have function tracer define options per instance tracing: Have function graph tracer define options per instance ---- kernel/trace/trace.c | 257 +++++++++++++++++++++++++---------- kernel/trace/trace.h | 3 + kernel/trace/trace_functions.c | 10 +- kernel/trace/trace_functions_graph.c | 18 ++- 4 files changed, 202 insertions(+), 86 deletions(-)
