Re: [Intel-gfx] [PATCH v2] component: do not leave master devres group open after bind

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Oct 06, 2021 at 04:47:57PM +0300, Kai Vehmanen wrote:
> Hi,
> 
> On Tue, 5 Oct 2021, Greg KH wrote:
> 
> > On Wed, Sep 22, 2021 at 11:54:32AM +0300, Kai Vehmanen wrote:
> > > In current code, the devres group for aggregate master is left open
> > > after call to component_master_add_*(). This leads to problems when the
> > > master does further managed allocations on its own. When any
> > > participating driver calls component_del(), this leads to immediate
> > > release of resources.
> [...]
> > > the devres group, and by closing the devres group after
> > > the master->ops->bind() call is done. This allows devres allocations
> > > done by the driver acting as master to be isolated from the binding state
> > > of the aggregate driver. This modifies the logic originally introduced in
> > > commit 9e1ccb4a7700 ("drivers/base: fix devres handling for master device")
> > > 
> > > BugLink: https://gitlab.freedesktop.org/drm/intel/-/issues/4136
> > > Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
> > > Acked-by: Imre Deak <imre.deak@intel.com>
> > > Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> > 
> > What commit does this "fix:"?  And does it need to go to stable
> > kernel(s)?
> 
> I didn't put a "Fixes" on the original commit 9e1ccb4a7700 
> ("drivers/base: fix devres handling for master device") as it alone
> didn't cause problems. It did open the door for possible devres issues
> for anybody calling component_master_add_().
> 
> On audio side, this surfaced with the more recent commit 3fcaf24e5dce 
> ("ALSA: hda: Allocate resources with device-managed APIs"). In theory one 
> could have hit issues already before, but this made it very easy to hit
> on actual systems.
> 
> If I'd have to pick one, it would be 9e1ccb4a7700 ("drivers/base: fix 
> devres handling for master device"). And yes, given comments on this 
> thread, I'd say this needs to go to stable kernels.

Then please add a fixes: line and a cc: stable line and resend.

thanks,

greg k-h