linux-kernel - Re: [alsa-devel] [Xen-devel][PATCH 3/3] ALSA: xen-front: Use Xen common shared buffer implementation

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Date:   Thu, 22 Nov 2018 16:47:14 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Oleksandr Andrushchenko <andr2000@...il.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, alsa-devel@...a-project.org,
        jgross@...e.com, boris.ostrovsky@...cle.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [alsa-devel] [Xen-devel][PATCH 3/3] ALSA: xen-front: Use Xen common        shared buffer implementation

On Thu, 22 Nov 2018 11:02:30 +0100,
Oleksandr Andrushchenko wrote:
> 
> @@ -214,12 +221,19 @@ static void stream_clear(struct xen_snd_front_pcm_stream_info *stream)
>  	stream->out_frames = 0;
>  	atomic_set(&stream->hw_ptr, 0);
>  	xen_snd_front_evtchnl_pair_clear(stream->evt_pair);
> -	xen_snd_front_shbuf_clear(&stream->sh_buf);
> +	memset(&stream->shbuf, 0, sizeof(stream->shbuf));
> +	stream->buffer = NULL;
> +	stream->buffer_sz = 0;
> +	stream->pages = NULL;
> +	stream->num_pages = 0;
>  }
>  
>  static void stream_free(struct xen_snd_front_pcm_stream_info *stream)
>  {
> -	xen_snd_front_shbuf_free(&stream->sh_buf);
> +	xen_front_pgdir_shbuf_unmap(&stream->shbuf);
> +	xen_front_pgdir_shbuf_free(&stream->shbuf);
> +	free_pages_exact(stream->buffer, stream->buffer_sz);
> +	kfree(stream->pages);
>  	stream_clear(stream);
>  }
>  
> @@ -421,10 +435,34 @@ static int alsa_close(struct snd_pcm_substream *substream)
>  	return 0;
>  }
>  
> +static int shbuf_setup_backstore(struct xen_snd_front_pcm_stream_info *stream,
> +				 size_t buffer_sz)
> +{
> +	int i;
> +
> +	stream->buffer_sz = buffer_sz;
> +	stream->buffer = alloc_pages_exact(stream->buffer_sz, GFP_KERNEL);
> +	if (!stream->buffer)
> +		return -ENOMEM;

This keeps the NULL stream->buffer, and then the caller goes to the
error path via stream_free() which will lead to an Oops due to the
unconditional call of free_pages_exact().


thanks,

Takashi