Re: [Qemu-devel] Discussion: vnc: memory leak in zrle_compress_data

[Gerd Hoffmann]

On Sun, Sep 01, 2019 at 10:43:42PM +0800, Li Qiang wrote:
> fangying <address@hidden> 于2019年9月1日周日 下午8:29写道：
> 
> > Nice work, your patch does fix this issue in my test.
> >
> > I think we should make VncState.zlib to be a pointer type as well.
> >
> > Since we are going to use pointers instead of copy, we must make sure that
> > there’s no race condition of pointer members between the local vs (vnc
> > worker thread) and origin vs (main thread).
> >
> >
> 
> Yes, there is a race between the main thread and vnc thread.

Where do you see a race?  The main thread allocates the data structures
before any job is started, cleans up after the jobs have been stopped
and never accesses them otherwise.

So unless I missed something the data structures are never accessed in
parallel from multiple threads.

> Maybe we should add a lock just like the 'vs->output_mutex'.

output is a different story.  The output buffer is accessed in parallel
(job thread produces and main thread consumes), so we actually need a
lock here for synchronization.

cheers,
  Gerd