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SubjectRe: [PATCH 4/5] jump label: tracepoint support
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On Mon, 2010-03-22 at 12:07 -0400, Jason Baron wrote:
> Make use of the jump label infrastructure for tracepoints.
>
> Signed-off-by: Jason Baron <jbaron@redhat.com>
> ---
> include/linux/tracepoint.h | 34 +++++++++++++++++++---------------
> kernel/tracepoint.c | 8 ++++++++
> 2 files changed, 27 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index f59604e..c18b9c0 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -16,6 +16,7 @@
>
> #include <linux/types.h>
> #include <linux/rcupdate.h>
> +#include <linux/jump_label.h>
>
> struct module;
> struct tracepoint;
> @@ -63,20 +64,22 @@ struct tracepoint {
> * not add unwanted padding between the beginning of the section and the
> * structure. Force alignment to the same alignment as the section start.
> */
> -#define DECLARE_TRACE(name, proto, args) \
> - extern struct tracepoint __tracepoint_##name; \
> - static inline void trace_##name(proto) \
> - { \
> - if (unlikely(__tracepoint_##name.state)) \
> - __DO_TRACE(&__tracepoint_##name, \
> - TP_PROTO(proto), TP_ARGS(args)); \
> - } \
> - static inline int register_trace_##name(void (*probe)(proto)) \
> - { \
> - return tracepoint_probe_register(#name, (void *)probe); \
> - } \
> - static inline int unregister_trace_##name(void (*probe)(proto)) \
> - { \
> +#define DECLARE_TRACE(name, proto, args) \
> + extern struct tracepoint __tracepoint_##name; \
> + static inline void trace_##name(proto) \
> + { \
> + JUMP_LABEL(name, do_trace, __tracepoint_##name.state); \
> + return; \
> +do_trace: \
> + __DO_TRACE(&__tracepoint_##name, \
> + TP_PROTO(proto), TP_ARGS(args)); \

Does this still work on all archs, and when jump labels are not
supported?

I may have missed a patch (I have not received patch 2 yet).

-- Steve

> + } \
> + static inline int register_trace_##name(void (*probe)(proto)) \
> + { \
> + return tracepoint_probe_register(#name, (void *)probe); \
> + } \
> + static inline int unregister_trace_##name(void (*probe)(proto)) \
> + { \
> return tracepoint_probe_unregister(#name, (void *)probe);\
> }
>
> @@ -86,7 +89,8 @@ struct tracepoint {
> __attribute__((section("__tracepoints_strings"))) = #name; \
> struct tracepoint __tracepoint_##name \
> __attribute__((section("__tracepoints"), aligned(32))) = \
> - { __tpstrtab_##name, 0, reg, unreg, NULL }
> + { __tpstrtab_##name, 0, reg, unreg, NULL }; \
> + DEFINE_JUMP_LABEL(name);
>
> #define DEFINE_TRACE(name) \
> DEFINE_TRACE_FN(name, NULL, NULL);
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index cc89be5..8acced8 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -25,6 +25,7 @@
> #include <linux/err.h>
> #include <linux/slab.h>
> #include <linux/sched.h>
> +#include <linux/jump_label.h>
>
> extern struct tracepoint __start___tracepoints[];
> extern struct tracepoint __stop___tracepoints[];
> @@ -256,6 +257,10 @@ static void set_tracepoint(struct tracepoint_entry **entry,
> * is used.
> */
> rcu_assign_pointer(elem->funcs, (*entry)->funcs);
> + if (!elem->state && active)
> + enable_jump_label(elem->name);
> + if (elem->state && !active)
> + disable_jump_label(elem->name);
> elem->state = active;
> }
>
> @@ -270,6 +275,9 @@ static void disable_tracepoint(struct tracepoint *elem)
> if (elem->unregfunc && elem->state)
> elem->unregfunc();
>
> + if (elem->state)
> + disable_jump_label(elem->name);
> +
> elem->state = 0;
> rcu_assign_pointer(elem->funcs, NULL);
> }




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