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SubjectRe: [PATCH v10 1/1] Tracepoint: register/unregister struct tracepoint
On Fri,  4 Apr 2014 10:02:34 -0400
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> Register/unregister tracepoint probes with struct tracepoint pointer
> rather than tracepoint name.
>
> This change, which vastly simplifies tracepoint.c, has been proposed by
> Steven Rostedt. It also removes 8.8kB (mostly of text) to the vmlinux
> size.
>
> >From this point on, the tracers need to pass a struct tracepoint pointer
> to probe register/unregister. A probe can now only be connected to a
> tracepoint that exists. Moreover, tracers are responsible for
> unregistering the probe before the module containing its associated
> tracepoint is unloaded.
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> CC: Steven Rostedt <rostedt@goodmis.org>
> CC: Ingo Molnar <mingo@kernel.org>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Frank Ch. Eigler <fche@redhat.com>
> CC: Johannes Berg <johannes.berg@intel.com>
> ---
> include/linux/ftrace_event.h | 22 +-
> include/linux/tracepoint.h | 41 +--
> include/trace/ftrace.h | 9 +-
> kernel/trace/trace_events.c | 51 ++--
> kernel/trace/trace_events_trigger.c | 2 +-
> kernel/trace/trace_kprobe.c | 21 +-
> kernel/trace/trace_output.c | 2 +-
> kernel/trace/trace_uprobe.c | 20 +-
> kernel/tracepoint.c | 509 +++++++++++++++--------------------
> 9 files changed, 328 insertions(+), 349 deletions(-)
>
> diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
> index cdc3011..75e64e8 100644
> --- a/include/linux/ftrace_event.h
> +++ b/include/linux/ftrace_event.h
> @@ -7,6 +7,7 @@
> #include <linux/percpu.h>
> #include <linux/hardirq.h>
> #include <linux/perf_event.h>
> +#include <linux/tracepoint.h>
>
> struct trace_array;
> struct trace_buffer;
> @@ -232,6 +233,7 @@ enum {
> TRACE_EVENT_FL_IGNORE_ENABLE_BIT,
> TRACE_EVENT_FL_WAS_ENABLED_BIT,
> TRACE_EVENT_FL_USE_CALL_FILTER_BIT,
> + TRACE_EVENT_FL_TRACEPOINT_BIT,
> };
>
> /*
> @@ -244,6 +246,7 @@ enum {
> * (used for module unloading, if a module event is enabled,
> * it is best to clear the buffers that used it).
> * USE_CALL_FILTER - For ftrace internal events, don't use file filter
> + * TRACEPOINT - Event is a tracepoint
> */
> enum {
> TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT),
> @@ -252,12 +255,17 @@ enum {
> TRACE_EVENT_FL_IGNORE_ENABLE = (1 << TRACE_EVENT_FL_IGNORE_ENABLE_BIT),
> TRACE_EVENT_FL_WAS_ENABLED = (1 << TRACE_EVENT_FL_WAS_ENABLED_BIT),
> TRACE_EVENT_FL_USE_CALL_FILTER = (1 << TRACE_EVENT_FL_USE_CALL_FILTER_BIT),
> + TRACE_EVENT_FL_TRACEPOINT = (1 << TRACE_EVENT_FL_TRACEPOINT_BIT),
> };
>
> struct ftrace_event_call {
> struct list_head list;
> struct ftrace_event_class *class;
> - char *name;
> + union {
> + char *name;
> + /* Set TRACE_EVENT_FL_TRACEPOINT flag when using "tp" */
> + struct tracepoint *tp;
> + };
> struct trace_event event;
> const char *print_fmt;
> struct event_filter *filter;
> @@ -271,6 +279,7 @@ struct ftrace_event_call {
> * bit 3: ftrace internal event (do not enable)
> * bit 4: Event was enabled by module
> * bit 5: use call filter rather than file filter
> + * bit 6: Event is a tracepoint
> */
> int flags; /* static flags of different events */
>
> @@ -283,6 +292,15 @@ struct ftrace_event_call {
> #endif
> };
>
> +static inline const char *
> +ftrace_event_get_name(struct ftrace_event_call *call)

I was thinking about this, and it really should be called
"ftrace_event_name()", the "get" implies that there should be an
associated "put".

> +{
> + if (call->flags & TRACE_EVENT_FL_TRACEPOINT)
> + return call->tp ? call->tp->name : NULL;
> + else
> + return call->name;
> +}

Also, you missed a bunch of conversions in trace_event.c file. Do a
search for '->name' and you'll find them. The ones that shouldn't be
converted are rather obvious (system, field, mod), but you'll see
others that were missed. I'm a bit nervous about what other ones may be
missed as well.

-- Steve


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