On Tue, 5 Sep 2017 16:57:37 -0500 Tom Zanussi <[email protected]> wrote:
> The tracepoint infrastructure assumes statically-defined tracepoints > and uses static_keys for tracepoint enablement. In order to define > tracepoints on the fly, we need to have a dynamic counterpart. Do we? I believe the static keys should work just fine if you don't have any defined static keys jumps, and they should work as a simple counter. Could we do that instead of adding another variable to a structure that is defined over a thousand times? Save us 4k of memory. -- Steve > > Add a 'dynamic' flag to struct tracepoint along with accompanying > logic for this purpose. > > Signed-off-by: Tom Zanussi <[email protected]> > --- > include/linux/tracepoint-defs.h | 1 + > kernel/tracepoint.c | 18 +++++++++++++----- > 2 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h > index a031920..bc22d54 100644 > --- a/include/linux/tracepoint-defs.h > +++ b/include/linux/tracepoint-defs.h > @@ -32,6 +32,7 @@ struct tracepoint { > int (*regfunc)(void); > void (*unregfunc)(void); > struct tracepoint_func __rcu *funcs; > + bool dynamic; > }; > > #endif > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c > index 685c50a..1c5957f 100644 > --- a/kernel/tracepoint.c > +++ b/kernel/tracepoint.c > @@ -197,7 +197,9 @@ static int tracepoint_add_func(struct tracepoint *tp, > struct tracepoint_func *old, *tp_funcs; > int ret; > > - if (tp->regfunc && !static_key_enabled(&tp->key)) { > + if (tp->regfunc && > + ((tp->dynamic && !(atomic_read(&tp->key.enabled) > 0)) || > + !static_key_enabled(&tp->key))) { > ret = tp->regfunc(); > if (ret < 0) > return ret; > @@ -219,7 +221,9 @@ static int tracepoint_add_func(struct tracepoint *tp, > * is used. > */ > rcu_assign_pointer(tp->funcs, tp_funcs); > - if (!static_key_enabled(&tp->key)) > + if (tp->dynamic && !(atomic_read(&tp->key.enabled) > 0)) > + atomic_inc(&tp->key.enabled); > + else if (!tp->dynamic && !static_key_enabled(&tp->key)) > static_key_slow_inc(&tp->key); > release_probes(old); > return 0; > @@ -246,10 +250,14 @@ static int tracepoint_remove_func(struct tracepoint *tp, > > if (!tp_funcs) { > /* Removed last function */ > - if (tp->unregfunc && static_key_enabled(&tp->key)) > + if (tp->unregfunc && > + ((tp->dynamic && (atomic_read(&tp->key.enabled) > 0)) || > + static_key_enabled(&tp->key))) > tp->unregfunc(); > > - if (static_key_enabled(&tp->key)) > + if (tp->dynamic && (atomic_read(&tp->key.enabled) > 0)) > + atomic_dec(&tp->key.enabled); > + else if (!tp->dynamic && static_key_enabled(&tp->key)) > static_key_slow_dec(&tp->key); > } > rcu_assign_pointer(tp->funcs, tp_funcs); > @@ -258,7 +266,7 @@ static int tracepoint_remove_func(struct tracepoint *tp, > } > > /** > - * tracepoint_probe_register - Connect a probe to a tracepoint > + * tracepoint_probe_register_prio - Connect a probe to a tracepoint > * @tp: tracepoint > * @probe: probe handler > * @data: tracepoint data
