[gst-devel] thread unsafety in gst_pad_get_internal_links()

[Olivier Crête]

On Tue, 2008-08-26 at 10:46 +0800, Eric Zhang wrote:
> Hi, gstreamer-devel:
> 
>     `gst_pad_get_internal_links' just call the `intlinkfunc' function 
> pointer which is set by user by calling 
> `gst_pad_set_internal_link_function'. And the lock is suppose to be set 
> on user's `internal_link' function, so I think there is no need to set 
> lock in `gst_pad_get_internal_links'.

I'm not talking about the gst_pad_get_internal_links(), but about its
default implementation.. (and about the fact that the returned pads dont
have their refcount increased).

Olivier


> Olivier Crête wrote:
> > Hello,
> >
> > I just noticed that gst_pad_get_internal_links() is not thread safe. It
> > does not take the object lock while looking up the list of pads and does
> > not reference the pads. So its very possible that it could happen in the
> > middle of a modification of the list (lets say if I add a pad to a tee).
> > Or that the pad could be gone by the time I get to do something with it.
> >
> > I propose deprecating it (since we can't modify it without breaking the
> > ABI) and add a new call get_internal_links_safe() that will returns a
> > list of refed pads. And fixing the default implementation of boths to be
> > thread safe (and probably having the default implementation of the
> > unsafe version call the safe version and unref the pads).
> >
> >   
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-- 
Olivier Crête
olivier.crete at collabora.co.uk
Collabora Ltd
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