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authorMark Brown <broonie@kernel.org>2021-10-08 16:31:57 +0300
committerMark Brown <broonie@kernel.org>2021-10-14 14:47:29 +0300
commit6098475d4cb48d821bdf453c61118c56e26294f0 (patch)
treeddd30f9c1cc1ffc9e4f9e1fcb3fe4abc53d2b121 /drivers/spi
parent75b3cb97eb1f05042745c0655a7145b0262d4c5c (diff)
downloadlinux-6098475d4cb48d821bdf453c61118c56e26294f0.tar.xz
spi: Fix deadlock when adding SPI controllers on SPI buses
Currently we have a global spi_add_lock which we take when adding new devices so that we can check that we're not trying to reuse a chip select that's already controlled. This means that if the SPI device is itself a SPI controller and triggers the instantiation of further SPI devices we trigger a deadlock as we try to register and instantiate those devices while in the process of doing so for the parent controller and hence already holding the global spi_add_lock. Since we only care about concurrency within a single SPI bus move the lock to be per controller, avoiding the deadlock. This can be easily triggered in the case of spi-mux. Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/spi.c17
1 files changed, 6 insertions, 11 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index aea037c65985..412a10586233 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -478,12 +478,6 @@ static LIST_HEAD(spi_controller_list);
*/
static DEFINE_MUTEX(board_lock);
-/*
- * Prevents addition of devices with same chip select and
- * addition of devices below an unregistering controller.
- */
-static DEFINE_MUTEX(spi_add_lock);
-
/**
* spi_alloc_device - Allocate a new SPI device
* @ctlr: Controller to which device is connected
@@ -636,9 +630,9 @@ int spi_add_device(struct spi_device *spi)
* chipselect **BEFORE** we call setup(), else we'll trash
* its configuration. Lock against concurrent add() calls.
*/
- mutex_lock(&spi_add_lock);
+ mutex_lock(&ctlr->add_lock);
status = __spi_add_device(spi);
- mutex_unlock(&spi_add_lock);
+ mutex_unlock(&ctlr->add_lock);
return status;
}
EXPORT_SYMBOL_GPL(spi_add_device);
@@ -658,7 +652,7 @@ static int spi_add_device_locked(struct spi_device *spi)
/* Set the bus ID string */
spi_dev_set_name(spi);
- WARN_ON(!mutex_is_locked(&spi_add_lock));
+ WARN_ON(!mutex_is_locked(&ctlr->add_lock));
return __spi_add_device(spi);
}
@@ -2830,6 +2824,7 @@ int spi_register_controller(struct spi_controller *ctlr)
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)
@@ -2966,7 +2961,7 @@ void spi_unregister_controller(struct spi_controller *ctlr)
/* Prevent addition of new devices, unregister existing ones */
if (IS_ENABLED(CONFIG_SPI_DYNAMIC))
- mutex_lock(&spi_add_lock);
+ mutex_lock(&ctlr->add_lock);
device_for_each_child(&ctlr->dev, NULL, __unregister);
@@ -2997,7 +2992,7 @@ void spi_unregister_controller(struct spi_controller *ctlr)
mutex_unlock(&board_lock);
if (IS_ENABLED(CONFIG_SPI_DYNAMIC))
- mutex_unlock(&spi_add_lock);
+ mutex_unlock(&ctlr->add_lock);
}
EXPORT_SYMBOL_GPL(spi_unregister_controller);