Re: [PATCH 08/17] drm/i915: Drop spinlocks around adding to the client request list

Chris Wilson
2016-09-02T11:02:43Z

On Fri, Sep 02, 2016 at 11:59:12AM +0100, Chris Wilson wrote:
> On Fri, Sep 02, 2016 at 11:30:18AM +0100, John Harrison wrote:
> > >+ if (request->file_priv) {
> > Why check for request->file_priv again? The block above will exit if
> > it is null. There surely can't be a race with remove_from_client
> > being called concurrently with add_to_client? Especially as
> > add_to_client no longer takes the spin_lock anyway.
>
> We can however allow i915_gem_release() to be called concurrently. It
> doesn't require struct_mutex.

That's not correct. setting file_priv = NULL is serialised by the
struct_mutex, not the file_priv->mm.lock. That spin_lock there is
misleading.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre