[FFmpeg-devel] [PATCH v4 1/1] avutils/hwcontext: When deriving a hwdevice, search for existing device in both directions

[Soft Works]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Soft Works
> Sent: Friday, November 26, 2021 8:29 PM
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH v4 1/1] avutils/hwcontext: When deriving a
> hwdevice, search for existing device in both directions
> 
> 
> 
> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Anton
> > Khirnov
> > Sent: Friday, November 26, 2021 8:12 PM
> > To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> > Subject: Re: [FFmpeg-devel] [PATCH v4 1/1] avutils/hwcontext: When deriving
> a
> > hwdevice, search for existing device in both directions
> >
> > Quoting Soft Works (2021-11-26 19:43:58)
> > > Maybe I'm missing something, but hw device contexts are refcounted.
> > > What happens in hwdevice_ctx_free() is this:
> > >
> > > av_buffer_unref(&ctx->internal->source_device);
> >
> > IIUC this only happens after the parent device is freed. My concern is
> > the following situation:
> > - the caller creates a parent hwdevice
> > - the caller derives a child from it, which may acquire some additional
> >   resources beyond what the parent holds
> > - the caller unrefs all his references to the child, but the child does
> >   not get freed because the parent still holds a reference to it

BTW, that's the current behavior anyway. The only change that this patch 
is adding is to find _all_ existing derived contexts, by iterating through
the whole tree of derivations instead of just following the parent direction.

softworkz