Re: [PATCH] tracing: Sample module to demonstrate kernel access to Ftrace instances.

[Steven Rostedt]

On Fri, 20 Sep 2019 16:59:26 -0700
Divya Indi <divya.indi@xxxxxxxxxx> wrote:

> This is a sample module to demostrate the use of the newly introduced and
> exported APIs to access Ftrace instances from within the kernel.
> 
> Newly introduced APIs used here -
> 
> 1. Create a new trace array if it does not exist.
> struct trace_array *trace_array_create(const char *name)
> 
> 2. Destroy/Remove a trace array.
> int trace_array_destroy(struct trace_array *tr)
> 
> 3. Lookup a trace array, given its name.
> struct trace_array *trace_array_lookup(const char *name)
> 
> 4. Enable/Disable trace events:
> int trace_array_set_clr_event(struct trace_array *tr, const char *system,
>         const char *event, int set);
> 
> Exported APIs -
> 1. trace_printk equivalent for instances.
> int trace_array_printk(struct trace_array *tr,
>                unsigned long ip, const char *fmt, ...);
> 
> 2. Helper function.
> void trace_printk_init_buffers(void);
> 
> 3. To decrement the reference counter.
> void trace_array_put(struct trace_array *tr)
> 
> Signed-off-by: Divya Indi <divya.indi@xxxxxxxxxx>
> Reviewed-by: Manjunath Patil <manjunath.b.patil@xxxxxxxxxx>
> Reviewed-by: Joe Jin <joe.jin@xxxxxxxxxx>
> ---
>  samples/Kconfig                              |   7 ++
>  samples/Makefile                             |   1 +
>  samples/ftrace_instance/Makefile             |   6 ++
>  samples/ftrace_instance/sample-trace-array.c | 134 +++++++++++++++++++++++++++
>  samples/ftrace_instance/sample-trace-array.h |  84 +++++++++++++++++
>  5 files changed, 232 insertions(+)
>  create mode 100644 samples/ftrace_instance/Makefile
>  create mode 100644 samples/ftrace_instance/sample-trace-array.c
>  create mode 100644 samples/ftrace_instance/sample-trace-array.h
>

I applied this patch but get this:

/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âmytimer_handlerâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:35:2: error: implicit declaration of function âtrace_array_set_clr_eventâ; did you mean âtrace_set_clr_eventâ? [-Werror=implicit-function-declaration]
  trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", 0);
  ^~~~~~~~~~~~~~~~~~~~~~~~~
  trace_set_clr_event
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsimple_thread_funcâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:47:2: error: implicit declaration of function âtrace_array_printkâ; did you mean âtrace_seq_printfâ? [-Werror=implicit-function-declaration]
  trace_array_printk(tr, _THIS_IP_, "trace_array_printk: count=%d\n",
  ^~~~~~~~~~~~~~~~~~
  trace_seq_printf
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsimple_threadâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:85:2: error: implicit declaration of function âtrace_array_putâ; did you mean âtrace_seq_putcâ? [-Werror=implicit-function-declaration]
  trace_array_put(tr);
  ^~~~~~~~~~~~~~~
  trace_seq_putc
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsample_trace_array_initâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:100:7: error: implicit declaration of function âtrace_array_lookupâ; did you mean âradix_tree_lookupâ? [-Werror=implicit-function-declaration]
  tr = trace_array_lookup("sample-instance");
       ^~~~~~~~~~~~~~~~~~
       radix_tree_lookup
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:100:5: warning: assignment to âstruct trace_array *â from âintâ makes pointer from integer without a cast [-Wint-conversion]
  tr = trace_array_lookup("sample-instance");
     ^
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:102:8: error: implicit declaration of function âtrace_array_createâ; did you mean âftrace_force_updateâ? [-Werror=implicit-function-declaration]
   tr = trace_array_create("sample-instance");
        ^~~~~~~~~~~~~~~~~~
        ftrace_force_update
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:102:6: warning: assignment to âstruct trace_array *â from âintâ makes pointer from integer without a cast [-Wint-conversion]
   tr = trace_array_create("sample-instance");
      ^
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:110:2: error: implicit declaration of function âtrace_printk_init_buffersâ; did you mean âtrace_event_get_offsetsâ? [-Werror=implicit-function-declaration]
  trace_printk_init_buffers();
  ^~~~~~~~~~~~~~~~~~~~~~~~~
  trace_event_get_offsets
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsample_trace_array_exitâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:126:2: error: implicit declaration of function âtrace_array_destroyâ; did you mean âassoc_array_destroyâ? [-Werror=implicit-function-declaration]
  trace_array_destroy(tr);
  ^~~~~~~~~~~~~~~~~~~
  assoc_array_destroy
cc1: some warnings being treated as errors
make[3]: *** [/work/git/linux-trace.git/scripts/Makefile.build:266: samples/ftrace_instance/sample-trace-array.o] Error 1
make[2]: *** [/work/git/linux-trace.git/scripts/Makefile.build:509: samples/ftrace_instance] Error 2
make[1]: *** [/work/git/linux-trace.git/Makefile:1650: samples] Error 2
make[1]: *** Waiting for unfinished jobs....


-- Steve