Unverified Commit 16a8e2fb authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Mark Brown
Browse files

spi-mux: Fix false-positive lockdep splats 



io_mutex is taken by spi_setup() and spi-mux's .setup() callback calls
spi_setup() which results in a nested lock of io_mutex.

add_lock is taken by spi_add_device(). The device_add() call in there
can result in calling spi-mux's .probe() callback which registers its
own spi controller which in turn results in spi_add_device() being
called again.

To fix this initialize the controller's locks already in
spi_alloc_controller() to give spi_mux_probe() a chance to set the
lockdep subclass.

Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20211013133710.2679703-2-u.kleine-koenig@pengutronix.de


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 6098475d

drivers/spi/spi-mux.c

+7 −0
Original line number Diff line number Diff line
@@ -137,6 +137,13 @@ static int spi_mux_probe(struct spi_device *spi) 
	priv = spi_controller_get_devdata(ctlr);

	priv->spi = spi;



	/*

	 * Increase lockdep class as these lock are taken while the parent bus

	 * already holds their instance's lock.

	 */

	lockdep_set_subclass(&ctlr->io_mutex, 1);

	lockdep_set_subclass(&ctlr->add_lock, 1);



	priv->mux = devm_mux_control_get(&spi->dev, NULL);

	if (IS_ERR(priv->mux)) {

		ret = dev_err_probe(&spi->dev, PTR_ERR(priv->mux),

drivers/spi/spi.c

+6 −6
Original line number Diff line number Diff line
@@ -2547,6 +2547,12 @@ struct spi_controller *__spi_alloc_controller(struct device *dev, 
		return NULL;



	device_initialize(&ctlr->dev);

	INIT_LIST_HEAD(&ctlr->queue);

	spin_lock_init(&ctlr->queue_lock);

	spin_lock_init(&ctlr->bus_lock_spinlock);

	mutex_init(&ctlr->bus_lock_mutex);

	mutex_init(&ctlr->io_mutex);

	mutex_init(&ctlr->add_lock);

	ctlr->bus_num = -1;

	ctlr->num_chipselect = 1;

	ctlr->slave = slave;
@@ -2819,12 +2825,6 @@ int spi_register_controller(struct spi_controller *ctlr) 
			return id;

		ctlr->bus_num = id;

	}

	INIT_LIST_HEAD(&ctlr->queue);

	spin_lock_init(&ctlr->queue_lock);

	spin_lock_init(&ctlr->bus_lock_spinlock);

	mutex_init(&ctlr->bus_lock_mutex);

	mutex_init(&ctlr->io_mutex);

	mutex_init(&ctlr->add_lock);

	ctlr->bus_lock_flag = 0;

	init_completion(&ctlr->xfer_completion);

	if (!ctlr->max_dma_len)