[vlc-devel] [PATCH 2/3] misc/xml: only initialize libxml2 once

[Rémi Denis-Courmont]

Hi,

Le keskiviikkona 23. syyskuuta 2020, 21.52.44 EEST Marvin Scholz a écrit :
> ---
>  modules/misc/xml/libxml.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/modules/misc/xml/libxml.c b/modules/misc/xml/libxml.c
> index e077139be7f..69637892be9 100644
> --- a/modules/misc/xml/libxml.c
> +++ b/modules/misc/xml/libxml.c
> @@ -52,7 +52,15 @@ static void CatalogAdd( xml_t *p_xml, const char
> *psz_arg1, (unsigned char*)psz_filename );
>  }
> 
> -static vlc_mutex_t lock = VLC_STATIC_MUTEX;
> +/**************************************************************************
> *** + * libxml2 initialization
> +
> ***************************************************************************
> **/ +static vlc_once_t xml_init_once_token = VLC_STATIC_ONCE;
> +
> +static void vlc_libxml_init_once(void)
> +{
> +    xmlInitParser();
> +}

If another non-concurrent piece of code initializes LibXML, uses it and 
deinitializes it, between two VLC uses then I think that this will break.

AFAIK, calling xmlInitParser() everytime is the least unsafe option.

> 
>  /**************************************************************************
> *** * Module initialization
> @@ -64,9 +72,7 @@ static int Open( vlc_object_t *p_this )
>      if( !xmlHasFeature( XML_WITH_THREAD ) )
>          return VLC_EGENERIC;
> 
> -    vlc_mutex_lock( &lock );
> -    xmlInitParser();
> -    vlc_mutex_unlock( &lock );
> +    vlc_once(&xml_init_once_token, vlc_libxml_init_once);
> 
>      p_xml->pf_catalog_load = CatalogLoad;
>      p_xml->pf_catalog_add  = CatalogAdd;
> @@ -232,9 +238,7 @@ static int ReaderOpen( vlc_object_t *p_this )
>      if( unlikely(!p_sys) )
>          return VLC_ENOMEM;
> 
> -    vlc_mutex_lock( &lock );
> -    xmlInitParser();
> -    vlc_mutex_unlock( &lock );
> +    vlc_once(&xml_init_once_token, vlc_libxml_init_once);
> 
>      p_libxml_reader = xmlReaderForIO( StreamRead, NULL, p_reader->p_stream,
> NULL, NULL, 0 );


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