Re: [RFC][PATCH v2] tracing: Add __bitmask() macro to trace events to cpumasks and other bitmasks

Javi Merino
2014-05-14T15:51:01Z

On Wed, May 14, 2014 at 04:36:23PM +0100, Steven Rostedt wrote:
> On Wed, 14 May 2014 15:23:24 +0100
> Javi Merino <javi.merino@arm.com> wrote:
>
> > > diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> > > index 0a1a4f7..d9c44af 100644
> > > --- a/include/trace/ftrace.h
> > > +++ b/include/trace/ftrace.h
> > > @@ -53,6 +53,9 @@
> > > #undef __string
> > > #define __string(item, src) __dynamic_array(char, item, -1)
> > >
> > > +#undef __bitmask
> > > +#define __bitmask(item, src) __dynamic_array(char, item, -1)
> > > +
> > > #undef TP_STRUCT__entry
> > > #define TP_STRUCT__entry(args...) args
> > >
> > > @@ -128,6 +131,9 @@
> > > #undef __string
> > > #define __string(item, src) __dynamic_array(char, item, -1)
> > >
> > > +#undef __string
> > > +#define __string(item, src) __dynamic_array(unsigned long, item, -1)
> > > +
> >
> > This overrides the previous definition of __string() and looks like it
> > shouldn't be here.
>
> Bah! I knew there was a reason I didn't push this out to my for-next
> branch yet. I can still rebase :-)
>
> That should have been __bitmask(). Hmm, amazing it still worked.
>
> >
> > > #undef DECLARE_EVENT_CLASS
> > > #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
> > > struct ftrace_data_offsets_##call { \
> > > @@ -200,6 +206,15 @@
> > > #undef __get_str
> > > #define __get_str(field) (char *)__get_dynamic_array(field)
> > >
> > > +#undef __get_bitmask
> > > +#define __get_bitmask(field) \
> > > + ({ \
> > > + void *__bitmask = __get_dynamic_array(field); \
> > > + unsigned int __bitmask_size; \
> > > + __bitmask_size = (__entry->__data_loc_##field >> 16) & 0xffff; \
> > > + ftrace_print_bitmask_seq(p, __bitmask, __bitmask_size); \
> > > + })
> > > +
> > > #undef __print_flags
> > > #define __print_flags(flag, delim, flag_array...) \
> > > ({ \
> > > @@ -322,6 +337,9 @@ static struct trace_event_functions ftrace_event_type_funcs_##call = { \
> > > #undef __string
> > > #define __string(item, src) __dynamic_array(char, item, -1)
> > >
> > > +#undef __bitmask
> > > +#define __bitmask(item, src) __dynamic_array(unsigned long, item, -1)
> > > +
> > >
> > > #undef DECLARE_EVENT_CLASS
> > > #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, func, print) \
> > > static int notrace __init \
> > > @@ -372,6 +390,29 @@ ftrace_define_fields_##call(struct ftrace_event_call *event_call) \
> > > #define __string(item, src) __dynamic_array(char, item, \
> > > strlen((src) ? (const char *)(src) : "(null)") + 1)
> > >
> > > +/*
> > > + * __bitmask_size_in_bytes_raw is the number of bytes needed to hold
> > > + * num_possible_cpus().
> > > + */
> > > +#define __bitmask_size_in_bytes_raw \
> > > + ((num_possible_cpus() + 7) / 8)
> > > +
> > > +#define __bitmask_size_in_longs \
> > > + ((__bitmask_size_in_bytes_raw + ((BITS_PER_LONG / 8) - 1)) \
> > > + / (BITS_PER_LONG / 8))
> > > +
> > > +/*
> > > + * __bitmask_size_in_bytes is the number of bytes needed to hold
> > > + * num_possible_cpus() padded out to the nearest long. This is what
> > > + * is saved in the buffer, just to be consistent.
> > > + */
> > > +#define __bitmask_size_in_bytes \
> > > + (__bitmask_size_in_longs * (BITS_PER_LONG / 8))
> > > +
> > > +#undef __bitmask
> > > +#define __bitmask(item, src) __dynamic_array(unsigned long, item, \
> > > + __bitmask_size_in_longs)
> > > +
> > > #undef DECLARE_EVENT_CLASS
> > > #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
> > > static inline notrace int ftrace_get_offsets_##call( \
> > > @@ -513,12 +554,22 @@ static inline notrace int ftrace_get_offsets_##call( \
> > > __entry->__data_loc_##item = __data_offsets.item;
> > >
> > > #undef __string
> > > -#define __string(item, src) __dynamic_array(char, item, -1) \
> > > +#define __string(item, src) __dynamic_array(char, item, -1)
> > >
> > > #undef __assign_str
> > > #define __assign_str(dst, src) \
> > > strcpy(__get_str(dst), (src) ? (const char *)(src) : "(null)");
> > >
> > > +#undef __bitmask
> > > +#define __bitmask(item, src) __dynamic_array(unsigned long, item, -1)
> >
> > Why src? It's not used in any of the definitions of the __bitmask()
> > macro, can we remove it?
>
> Hmm, I may need to refactor this. I may pull this patch for now to push
> the rest to for-next.
>
> I just noticed that we need a way to specify the length of the bitmask.
> Right now it's hardcoded as "num_possible_cpus", which Mathieu was
> asking for a more generic approach.
>
> OK, let me pull this patch out of my tree (thank god I never pushed
> it), and work on it a bit more.

Ok, well keep me posted on this, I've tried to use it but trace-cmd
says "[FAILED TO PARSE]" and I'm still trying to figure out if it's me
not using it properly or some bug in the code.

Cheers,
Javi