Re: [PATCH v2 dwarves 3/5] btf_encoder: rework btf_encoders__*() API to allow traversal of encoders

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Jan 30, 2023 at 02:29:43PM +0000, Alan Maguire wrote:
> To coordinate across multiple encoders at collection time, there
> will be a need to access the set of encoders.  Rework the unused
> btf_encoders__*() API to facilitate this.
> 
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> ---
>  btf_encoder.c | 30 ++++++++++++++++++++++--------
>  btf_encoder.h |  6 ------
>  2 files changed, 22 insertions(+), 14 deletions(-)
> 
> diff --git a/btf_encoder.c b/btf_encoder.c
> index 44f1905..e20b628 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -30,6 +30,7 @@
>  
>  #include <errno.h>
>  #include <stdint.h>
> +#include <pthread.h>
>  
>  struct elf_function {
>  	const char	*name;
> @@ -79,21 +80,32 @@ struct btf_encoder {
>  	} functions;
>  };
>  
> -void btf_encoders__add(struct list_head *encoders, struct btf_encoder *encoder)
> -{
> -	list_add_tail(&encoder->node, encoders);
> -}
> +static LIST_HEAD(encoders);
> +static pthread_mutex_t encoders__lock = PTHREAD_MUTEX_INITIALIZER;
>  
> -struct btf_encoder *btf_encoders__first(struct list_head *encoders)
> +/* mutex only needed for add/delete, as this can happen in multiple encoding
> + * threads.  Traversal of the list is currently confined to thread collection.
> + */
> +static void btf_encoders__add(struct btf_encoder *encoder)
>  {
> -	return list_first_entry(encoders, struct btf_encoder, node);
> +	pthread_mutex_lock(&encoders__lock);
> +	list_add_tail(&encoder->node, &encoders);
> +	pthread_mutex_unlock(&encoders__lock);
>  }
>  
> -struct btf_encoder *btf_encoders__next(struct btf_encoder *encoder)
> +#define btf_encoders__for_each_encoder(encoder)		\
> +	list_for_each_entry(encoder, &encoders, node)
> +
> +static void btf_encoders__delete(struct btf_encoder *encoder)
>  {
> -	return list_next_entry(encoder, node);
> +	pthread_mutex_lock(&encoders__lock);
> +	list_del(&encoder->node);
> +	pthread_mutex_unlock(&encoders__lock);
>  }
>  
> +#define btf_encoders__for_each_encoder(encoder)			\
> +	list_for_each_entry(encoder, &encoders, node)
> +

there's extra btf_encoders__for_each_encoder define

hum I'm scratching my head how this compile, probably because it's identical

jirka


>  #define PERCPU_SECTION ".data..percpu"
>  
>  /*
> @@ -1505,6 +1517,7 @@ struct btf_encoder *btf_encoder__new(struct cu *cu, const char *detached_filenam
>  
>  		if (encoder->verbose)
>  			printf("File %s:\n", cu->filename);
> +		btf_encoders__add(encoder);
>  	}
>  out:
>  	return encoder;
> @@ -1519,6 +1532,7 @@ void btf_encoder__delete(struct btf_encoder *encoder)
>  	if (encoder == NULL)
>  		return;
>  
> +	btf_encoders__delete(encoder);
>  	__gobuffer__delete(&encoder->percpu_secinfo);
>  	zfree(&encoder->filename);
>  	btf__free(encoder->btf);
> diff --git a/btf_encoder.h b/btf_encoder.h
> index a65120c..34516bb 100644
> --- a/btf_encoder.h
> +++ b/btf_encoder.h
> @@ -23,12 +23,6 @@ int btf_encoder__encode(struct btf_encoder *encoder);
>  
>  int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu, struct conf_load *conf_load);
>  
> -void btf_encoders__add(struct list_head *encoders, struct btf_encoder *encoder);
> -
> -struct btf_encoder *btf_encoders__first(struct list_head *encoders);
> -
> -struct btf_encoder *btf_encoders__next(struct btf_encoder *encoder);
> -
>  struct btf *btf_encoder__btf(struct btf_encoder *encoder);
>  
>  int btf_encoder__add_encoder(struct btf_encoder *encoder, struct btf_encoder *other);
> -- 
> 1.8.3.1
>