On Fri, Apr 2, 2021 at 4:20 PM Yordan Karadzhov (VMware)
<y.karadz@xxxxxxxxx> wrote:
>
> If the instance owns two mask objects, we no longer need to
> dynamically allocate memory in tracefs_options_get_supported() and
> tracefs_options_get_enabled(). This will simplify the code on the
> caller side, since the user is no longer responsible for freeing
> those masks.
>
> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@xxxxxxxxx>
> ---
> Documentation/libtracefs-option-get.txt | 4 +---
> include/tracefs.h | 6 +++---
> src/tracefs-instance.c | 24 ++++++++++++------------
> 3 files changed, 16 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/libtracefs-option-get.txt b/Documentation/libtracefs-option-get.txt
> index 9b3cb56..3290f24 100644
> --- a/Documentation/libtracefs-option-get.txt
> +++ b/Documentation/libtracefs-option-get.txt
> @@ -52,14 +52,13 @@ EXAMPLE
> --
> #include <tracefs.h>
> ...
> -struct tracefs_options_mask *options;
> +const struct tracefs_options_mask *options;
> ...
> options = tracefs_options_get_supported(NULL);
> if (!options) {
> /* Failed to get supported options */
> } else {
> ...
> - free(options);
> }
> ..
The description of the return value of tracefs_options_get_supported()
and tracefs_options_get_enabled() should be changed also, as it
suggests to free the return value;
> options = tracefs_options_get_enabled(NULL);
> @@ -67,7 +66,6 @@ if (!options) {
> /* Failed to get options, enabled in the top instance */
> } else {
> ...
> - free(options);
> }
> ...
>
> diff --git a/include/tracefs.h b/include/tracefs.h
> index 0665e8d..9efa91a 100644
> --- a/include/tracefs.h
> +++ b/include/tracefs.h
> @@ -132,11 +132,11 @@ enum tracefs_option_id {
> #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
>
> struct tracefs_options_mask;
> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
> enum tracefs_option_id id);
> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
> bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
> bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
> int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
> int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id);
> diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
> index 49645eb..9cb4b6d 100644
> --- a/src/tracefs-instance.c
> +++ b/src/tracefs-instance.c
> @@ -27,6 +27,8 @@ struct tracefs_instance {
> char *trace_dir;
> char *name;
> int flags;
> + struct tracefs_options_mask supported_opts;
> + struct tracefs_options_mask enabled_opts;
> };
>
> /**
> @@ -695,9 +697,8 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
> DIR *dir = NULL;
> long long val;
>
> - bitmask = calloc(1, sizeof(struct tracefs_options_mask));
> - if (!bitmask)
> - return NULL;
> + bitmask = enabled? &instance->enabled_opts : &instance->supported_opts;
This makes the API not thread safe. There should be no problem with
supported options, as they cannot be changed at runtime. I think it is
OK to limit the APIs , as I see no use case to call them from multiple
threads on the same instance, but this should be described in the
documentation.
> +
> dname = tracefs_instance_get_file(instance, "options");
> if (!dname)
> goto error;
> @@ -727,7 +728,6 @@ error:
> if (dir)
> closedir(dir);
> tracefs_put_tracing_file(dname);
> - free(bitmask);
> return NULL;
> }
>
> @@ -735,10 +735,10 @@ error:
> * tracefs_options_get_supported - Get all supported trace options in given instance
> * @instance: ftrace instance, can be NULL for the top instance
> *
> - * Returns allocated bitmask structure with all trace options, supported in given
> - * instance, or NULL in case of an error. The returned structure must be freed with free()
> + * Returns bitmask structure with all trace options, supported in given instance,
> + * or NULL in case of an error.
> */
> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
> {
> return trace_get_options(instance, false);
As supported options cannot be changed at runtime, they can be read
only once. The next calls can return the already initialised bitmask
with supported options.
> }
> @@ -747,10 +747,10 @@ struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instan
> * tracefs_options_get_enabled - Get all currently enabled trace options in given instance
> * @instance: ftrace instance, can be NULL for the top instance
> *
> - * Returns allocated bitmask structure with all trace options, enabled in given
> - * instance, or NULL in case of an error. The returned structure must be freed with free()
> + * Returns allocated bitmask structure with all trace options, enabled in given instance,
> + * or NULL in case of an error.
> */
> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
> {
> return trace_get_options(instance, true);
> }
> @@ -758,7 +758,7 @@ struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance
> static int trace_config_option(struct tracefs_instance *instance,
> enum tracefs_option_id id, bool set)
> {
> - char *set_str = set ? "1" : "0";
> + const char *set_str = set ? "1" : "0";
> char file[PATH_MAX];
> const char *name;
>
> @@ -846,7 +846,7 @@ bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_o
> * Returns true if an option with given id is set in the bitmask,
> * false if it is not set.
> */
> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
> enum tracefs_option_id id)
> {
> if (id > TRACEFS_OPTION_INVALID)
> --
> 2.27.0
>
--
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center
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