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

    Thanks,

    -- Steve



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