[PATCH 04/23] interconnect: imx: fix registration race

[Luca Ceresoli]

Hello Johan,

On Mon, 6 Feb 2023 09:09:50 +0100
Johan Hovold <johan at kernel.org> wrote:

> On Fri, Feb 03, 2023 at 05:01:21PM +0100, Luca Ceresoli wrote:
> > Hello Johan,
> > 
> > On Wed,  1 Feb 2023 11:15:40 +0100
> > Johan Hovold <johan+linaro at kernel.org> wrote:
> >   
> > > The current interconnect provider registration interface is inherently
> > > racy as nodes are not added until the after adding the provider. This
> > > can specifically cause racing DT lookups to fail.
> > > 
> > > Switch to using the new API where the provider is not registered until
> > > after it has been fully initialised.
> > > 
> > > Fixes: f0d8048525d7 ("interconnect: Add imx core driver")
> > > Cc: stable at vger.kernel.org      # 5.8
> > > Cc: Leonard Crestez <leonard.crestez at nxp.com>
> > > Cc: Alexandre Bailon <abailon at baylibre.com>
> > > Signed-off-by: Johan Hovold <johan+linaro at kernel.org>  
> > 
> > Georgi pointed me to this series after I reported a bug yesterday [0],
> > that I found on iMX8MP. So I ran some tests with my original, failing
> > tree, minus one patch with my debugging code to hunt for the bug, plus
> > patches 1-4 of this series.
> > 
> > The original code was failing approx 5~10% of the times. With your 4
> > patches applied it ran 139 times with zero errors, which looks great! I
> > won't be able to do more testing until next Monday to be extra sure.  
> 
> Thanks for testing.
> 
> It indeed looks like you're hitting the same race, and as the imx
> interconnect driver also initialises the provider data num_nodes count
> before adding the nodes it results in that NULL-deref (where the qcom
> driver failed a bit more gracefully).

My v6.2-rc5 tree with patches 1 to 4 added has booted 590 times with 0
errors, which add to the 139 times on Friday. This definitely deserves
my:

Tested-by: Luca Ceresoli <luca.ceresoli at bootlin.com>

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com