Re: [PATCH v3 4/5] libtracefs: Option's bit masks to be owned by the instance

[Tzvetomir Stoyanov <tz.stoyanov@gmail.com>]

On Thu, Apr 8, 2021 at 5:00 PM Yordan Karadzhov (VMware)
<y.karadz@gmail.com> 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@gmail.com>
> ---
>  Documentation/libtracefs-option-get.txt |  4 +---
>  include/tracefs-local.h                 |  8 ++++++++
>  include/tracefs.h                       |  2 +-
>  src/tracefs-instance.c                  | 15 +++++++++++++++
>  src/tracefs-tools.c                     | 24 ++++++++++++++----------
>  5 files changed, 39 insertions(+), 14 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);
>  }
>  ...
>  options = tracefs_options_get_enabled(NULL);
> @@ -67,7 +66,6 @@ if (!options) {
>         /* Failed to get options, enabled in the top instance */
>  } else {
>         ...
> -       free(options);
>  }
>  ...
The description in the "RETURN VALUE" section should be changed also,
as now it suggests to free the bitmask returned by those APIs.

>
> diff --git a/include/tracefs-local.h b/include/tracefs-local.h
> index 076b013..eb8c81b 100644
> --- a/include/tracefs-local.h
> +++ b/include/tracefs-local.h
> @@ -25,6 +25,8 @@ struct tracefs_instance {
>         int                     flags;
>         int                     ftrace_filter_fd;
>         int                     ftrace_notrace_fd;
> +       struct tracefs_options_mask     supported_opts;
> +       struct tracefs_options_mask     enabled_opts;
>  };
>
>  extern pthread_mutex_t toplevel_lock;
> @@ -48,4 +50,10 @@ char *trace_find_tracing_dir(void);
>  #define DEFFILEMODE (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH) /* 0666*/
>  #endif
>
> +struct tracefs_options_mask *
> +supported_opts_mask(struct tracefs_instance *instance);
> +
> +struct tracefs_options_mask *
> +enabled_opts_mask(struct tracefs_instance *instance);
> +
>  #endif /* _TRACE_FS_LOCAL_H */
> diff --git a/include/tracefs.h b/include/tracefs.h
> index e1fbef6..ea9dbd0 100644
> --- a/include/tracefs.h
> +++ b/include/tracefs.h
> @@ -132,7 +132,7 @@ 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);
>  bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
> diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
> index 599c3a7..74122aa 100644
> --- a/src/tracefs-instance.c
> +++ b/src/tracefs-instance.c
> @@ -21,6 +21,21 @@
>
>  #define FLAG_INSTANCE_NEWLY_CREATED    (1 << 0)
>
> +struct tracefs_options_mask    toplevel_supported_opts;
> +struct tracefs_options_mask    toplevel_enabled_opts;
> +
> +__hidden inline struct tracefs_options_mask *
> +supported_opts_mask(struct tracefs_instance *instance)
> +{
> +       return instance? &instance->supported_opts : &toplevel_supported_opts;
> +}
> +
> +__hidden inline struct tracefs_options_mask *
> +enabled_opts_mask(struct tracefs_instance *instance)
> +{
> +       return instance? &instance->enabled_opts : &toplevel_enabled_opts;
> +}
> +
>  /**
>   * instance_alloc - allocate a new ftrace instance
>   * @trace_dir - Full path to the tracing directory, where the instance is
> diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
> index fc9644a..b6967db 100644
> --- a/src/tracefs-tools.c
> +++ b/src/tracefs-tools.c
> @@ -211,6 +211,7 @@ enum tracefs_option_id tracefs_option_id(const char *name)
>  static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *instance,
>                                                       bool enabled)
>  {
> +       pthread_mutex_t *lock = instance ? &instance->lock : &toplevel_lock;
>         struct tracefs_options_mask *bitmask;
>         enum tracefs_option_id id;
>         char file[PATH_MAX];
> @@ -219,9 +220,6 @@ 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;
>         dname = tracefs_instance_get_file(instance, "options");
>         if (!dname)
>                 goto error;
> @@ -229,6 +227,11 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
>         if (!dir)
>                 goto error;
>
> +       bitmask = enabled? enabled_opts_mask(instance) :
> +                          supported_opts_mask(instance);
> +
> +       pthread_mutex_lock(lock);
> +       bitmask->mask = 0;
>         while ((dent = readdir(dir))) {
>                 if (*dent->d_name == '.')
>                         continue;
> @@ -242,6 +245,8 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
>                 if (id > TRACEFS_OPTION_INVALID)
>                         bitmask->mask |= (1ULL << (id - 1));
>         }
> +       pthread_mutex_unlock(lock);
> +
>         closedir(dir);
>         tracefs_put_tracing_file(dname);
>
> @@ -251,7 +256,6 @@ error:
>         if (dir)
>                 closedir(dir);
>         tracefs_put_tracing_file(dname);
> -       free(bitmask);
>         return NULL;
>  }
>
> @@ -259,8 +263,8 @@ 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)
>  {
> @@ -271,8 +275,8 @@ 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 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)
>  {
> @@ -282,7 +286,7 @@ 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;
>
> @@ -370,7 +374,7 @@ 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