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From:   Ioana Ciornei <ioana.ciornei@nxp.com>
To:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        Laurentiu Tudor <laurentiu.tudor@nxp.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] bus: fsl-mc: allocate resources when there is no scan in
 progress
Thread-Topic: [PATCH] bus: fsl-mc: allocate resources when there is no scan in
 progress
Thread-Index: AQHWL4qbnqBdRkT9Ok61D+CKMTFygKi4/0vw
Date:   Mon, 25 May 2020 16:13:23 +0000
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> Subject: [PATCH] bus: fsl-mc: allocate resources when there is no scan in
> progress
>=20
> Allocate resources from the fsl-mc bus only when a scan of the bus is not
> happening. This is useful when functional devices on the bus, such as DPN=
I,
> DPSW etc, request some kind of allocatable object but the scan of the bus=
 is still
> in progress, thus those resources are not yet available. Catch this early=
 and
> notify the upper layer driver of the condition.
>=20
> Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
> ---

Please don't apply this.
I just discovered a corner case in which this approach does not work.

Sorry for the bother,
Ioana

>  drivers/bus/fsl-mc/fsl-mc-allocator.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/bus/fsl-mc/fsl-mc-allocator.c b/drivers/bus/fsl-mc/f=
sl-mc-
> allocator.c
> index cc7bb900f524..794ddc9589dc 100644
> --- a/drivers/bus/fsl-mc/fsl-mc-allocator.c
> +++ b/drivers/bus/fsl-mc/fsl-mc-allocator.c
> @@ -184,6 +184,9 @@ int __must_check fsl_mc_resource_allocate(struct
> fsl_mc_bus *mc_bus,
>  	BUILD_BUG_ON(ARRAY_SIZE(fsl_mc_pool_type_strings) !=3D
>  		     FSL_MC_NUM_POOL_TYPES);
>=20
> +	if (!mutex_trylock(&mc_bus->scan_mutex))
> +		return -ENXIO;
> +
>  	*new_resource =3D NULL;
>  	if (pool_type < 0 || pool_type >=3D FSL_MC_NUM_POOL_TYPES)
>  		goto out;
> @@ -197,7 +200,7 @@ int __must_check fsl_mc_resource_allocate(struct
> fsl_mc_bus *mc_bus,
>  					    struct fsl_mc_resource, node);
>=20
>  	if (!resource) {
> -		error =3D -ENXIO;
> +		error =3D -ENOMEM;
>  		dev_err(&mc_bus_dev->dev,
>  			"No more resources of type %s left\n",
>  			fsl_mc_pool_type_strings[pool_type]);
> @@ -220,6 +223,7 @@ int __must_check fsl_mc_resource_allocate(struct
> fsl_mc_bus *mc_bus,
>  	mutex_unlock(&res_pool->mutex);
>  	*new_resource =3D resource;
>  out:
> +	mutex_unlock(&mc_bus->scan_mutex);
>  	return error;
>  }
>  EXPORT_SYMBOL_GPL(fsl_mc_resource_allocate);
> --
> 2.17.1