Extract callbacks and enabled state to non-packed structure

Atomic load/store should be performed on non-packed structure.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/side/trace.h b/include/side/trace.h
index f7bf90122cf5c4a4fffe5fedc99a9062c530d41e..8e0604d1c54c52b0838cd309304cfce11a5c2d30 100644 (file)
--- a/include/side/trace.h
+++ b/include/side/trace.h
@@ -650,19 +650,27 @@ struct side_tracer_dynamic_struct_visitor_ctx {
        void *priv;             /* Private tracer context. */
 } SIDE_PACKED;
 
+/*
+ * This structure is _not_ packed to allow atomic operations on its
+ * fields.
+ */
+struct side_event_state {
+       uintptr_t enabled;
+       const struct side_callback *callbacks;
+       uint32_t nr_callbacks;
+};
+
 struct side_event_description {
-       uintptr_t *enabled;
+       struct side_event_state *state;
        const char *provider_name;
        const char *event_name;
        const struct side_event_field *fields;
        const struct side_attr *attr;
-       const struct side_callback *callbacks;
        uint64_t flags;
        uint32_t version;
        uint32_t loglevel;      /* enum side_loglevel */
        uint32_t nr_fields;
        uint32_t nr_attr;
-       uint32_t nr_callbacks;
 } SIDE_PACKED;
 
 /* Event and type attributes */
@@ -1756,7 +1764,7 @@ struct side_event_description {
 #define side_arg_list(...)     __VA_ARGS__
 
 #define side_event_cond(_identifier) \
-       if (side_unlikely(__atomic_load_n(&side_event_enable__##_identifier, \
+       if (side_unlikely(__atomic_load_n(&side_event_state__##_identifier.enabled, \
                                        __ATOMIC_RELAXED)))
 
 #define side_event_call(_identifier, _sav) \
@@ -1795,21 +1803,24 @@ struct side_event_description {
                side_event_call_variadic(_identifier, SIDE_PARAM(_sav), SIDE_PARAM(_var), SIDE_PARAM_SELECT_ARG1(_, ##_attr, side_attr_list()))
 
 #define _side_define_event(_linkage, _identifier, _provider, _event, _loglevel, _fields, _flags, _attr...) \
-       _linkage uintptr_t side_event_enable__##_identifier __attribute__((section("side_event_enable"))); \
+       _linkage struct side_event_state __attribute__((section("side_event_state"))) \
+                       side_event_state__##_identifier = { \
+               .enabled = 0, \
+               .callbacks = &side_empty_callback, \
+               .nr_callbacks = 0, \
+       }; \
        _linkage struct side_event_description __attribute__((section("side_event_description"))) \
                        _identifier = { \
-               .enabled = &(side_event_enable__##_identifier), \
+               .state = &(side_event_state__##_identifier), \
                .provider_name = _provider, \
                .event_name = _event, \
                .fields = _fields, \
                .attr = SIDE_PARAM_SELECT_ARG1(_, ##_attr, side_attr_list()), \
-               .callbacks = &side_empty_callback, \
                .flags = (_flags), \
                .version = 0, \
                .loglevel = _loglevel, \
                .nr_fields = SIDE_ARRAY_SIZE(SIDE_PARAM(_fields)), \
                .nr_attr = SIDE_ARRAY_SIZE(SIDE_PARAM_SELECT_ARG1(_, ##_attr, side_attr_list())), \
-               .nr_callbacks = 0, \
        }; \
        static const struct side_event_description *side_event_ptr__##_identifier \
                __attribute__((section("side_event_description_ptr"), used)) = &(_identifier);
@@ -1839,7 +1850,7 @@ struct side_event_description {
                        _loglevel, SIDE_PARAM(_fields), SIDE_EVENT_FLAG_VARIADIC, SIDE_PARAM_SELECT_ARG1(_, ##_attr, side_attr_list()))
 
 #define side_declare_event(_identifier) \
-       extern uintptr_t side_event_enable_##_identifier; \
+       extern struct side_event_state side_event_state_##_identifier; \
        extern struct side_event_description _identifier
 
 #ifdef __cplusplus

diff --git a/src/side.c b/src/side.c
index 3b46f0e4bf9340efde1f27cf231320bf401ff753..3c0f1b2f3bb2f7b495822ac65c82947659fe107d 100644 (file)
--- a/src/side.c
+++ b/src/side.c
@@ -76,12 +76,12 @@ void side_call(const struct side_event_description *desc, const struct side_arg_
                printf("ERROR: unexpected variadic event description\n");
                abort();
        }
-       enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
+       enabled = __atomic_load_n(&desc->state->enabled, __ATOMIC_RELAXED);
        if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
                // TODO: call kernel write.
        }
        side_rcu_read_begin(&rcu_gp, &rcu_read_state);
-       for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++)
+       for (side_cb = side_rcu_dereference(desc->state->callbacks); side_cb->u.call != NULL; side_cb++)
                side_cb->u.call(desc, side_arg_vec, side_cb->priv);
        side_rcu_read_end(&rcu_gp, &rcu_read_state);
 }
@@ -102,12 +102,12 @@ void side_call_variadic(const struct side_event_description *desc,
                printf("ERROR: unexpected non-variadic event description\n");
                abort();
        }
-       enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
+       enabled = __atomic_load_n(&desc->state->enabled, __ATOMIC_RELAXED);
        if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
                // TODO: call kernel write.
        }
        side_rcu_read_begin(&rcu_gp, &rcu_read_state);
-       for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
+       for (side_cb = side_rcu_dereference(desc->state->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
                side_cb->u.call_variadic(desc, side_arg_vec, var_struct, side_cb->priv);
        side_rcu_read_end(&rcu_gp, &rcu_read_state);
 }
@@ -119,7 +119,7 @@ const struct side_callback *side_tracer_callback_lookup(
 {
        const struct side_callback *cb;
 
-       for (cb = desc->callbacks; cb->u.call != NULL; cb++) {
+       for (cb = desc->state->callbacks; cb->u.call != NULL; cb++) {
                if ((void *) cb->u.call == call && cb->priv == priv)
                        return cb;
        }
@@ -141,7 +141,7 @@ int _side_tracer_callback_register(struct side_event_description *desc,
        if (!initialized)
                side_init();
        pthread_mutex_lock(&side_lock);
-       old_nr_cb = desc->nr_callbacks;
+       old_nr_cb = desc->state->nr_callbacks;
        if (old_nr_cb == UINT32_MAX) {
                ret = SIDE_ERROR_INVAL;
                goto unlock;
@@ -151,7 +151,7 @@ int _side_tracer_callback_register(struct side_event_description *desc,
                ret = SIDE_ERROR_EXIST;
                goto unlock;
        }
-       old_cb = (struct side_callback *) desc->callbacks;
+       old_cb = (struct side_callback *) desc->state->callbacks;
        /* old_nr_cb + 1 (new cb) + 1 (NULL) */
        new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
        if (!new_cb) {
@@ -166,14 +166,14 @@ int _side_tracer_callback_register(struct side_event_description *desc,
                new_cb[old_nr_cb].u.call =
                        (side_tracer_callback_func) call;
        new_cb[old_nr_cb].priv = priv;
-       side_rcu_assign_pointer(desc->callbacks, new_cb);
+       side_rcu_assign_pointer(desc->state->callbacks, new_cb);
        side_rcu_wait_grace_period(&rcu_gp);
        if (old_nr_cb)
                free(old_cb);
-       desc->nr_callbacks++;
+       desc->state->nr_callbacks++;
        /* Increment concurrently with kernel setting the top bits. */
        if (!old_nr_cb)
-               (void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED);
+               (void) __atomic_add_fetch(&desc->state->enabled, 1, __ATOMIC_RELAXED);
 unlock:
        pthread_mutex_unlock(&side_lock);
        return ret;
@@ -218,12 +218,12 @@ static int _side_tracer_callback_unregister(struct side_event_description *desc,
                ret = SIDE_ERROR_NOENT;
                goto unlock;
        }
-       old_nr_cb = desc->nr_callbacks;
-       old_cb = (struct side_callback *) desc->callbacks;
+       old_nr_cb = desc->state->nr_callbacks;
+       old_cb = (struct side_callback *) desc->state->callbacks;
        if (old_nr_cb == 1) {
                new_cb = (struct side_callback *) &side_empty_callback;
        } else {
-               pos_idx = cb_pos - desc->callbacks;
+               pos_idx = cb_pos - desc->state->callbacks;
                /* Remove entry at pos_idx. */
                /* old_nr_cb - 1 (removed cb) + 1 (NULL) */
                new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
@@ -234,13 +234,13 @@ static int _side_tracer_callback_unregister(struct side_event_description *desc,
                memcpy(new_cb, old_cb, pos_idx);
                memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
        }
-       side_rcu_assign_pointer(desc->callbacks, new_cb);
+       side_rcu_assign_pointer(desc->state->callbacks, new_cb);
        side_rcu_wait_grace_period(&rcu_gp);
        free(old_cb);
-       desc->nr_callbacks--;
+       desc->state->nr_callbacks--;
        /* Decrement concurrently with kernel setting the top bits. */
        if (old_nr_cb == 1)
-               (void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
+               (void) __atomic_add_fetch(&desc->state->enabled, -1, __ATOMIC_RELAXED);
 unlock:
        pthread_mutex_unlock(&side_lock);
        return ret;
@@ -294,20 +294,20 @@ struct side_events_register_handle *side_events_register(struct side_event_descr
 static
 void side_event_remove_callbacks(struct side_event_description *desc)
 {
-       uint32_t nr_cb = desc->nr_callbacks;
+       uint32_t nr_cb = desc->state->nr_callbacks;
        struct side_callback *old_cb;
 
        if (!nr_cb)
                return;
-       old_cb = (struct side_callback *) desc->callbacks;
-       (void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
+       old_cb = (struct side_callback *) desc->state->callbacks;
+       (void) __atomic_add_fetch(&desc->state->enabled, -1, __ATOMIC_RELAXED);
        /*
         * Setting the state back to 0 cb and empty callbacks out of
         * caution. This should not matter because instrumentation is
         * unreachable.
         */
-       desc->nr_callbacks = 0;
-       side_rcu_assign_pointer(desc->callbacks, &side_empty_callback);
+       desc->state->nr_callbacks = 0;
+       side_rcu_assign_pointer(desc->state->callbacks, &side_empty_callback);
        /*
         * No need to wait for grace period because instrumentation is
         * unreachable.