5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mark Brown <broonie@xxxxxxxxxx>
commit 6098475d4cb48d821bdf453c61118c56e26294f0 upstream.
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@xxxxxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Hardik Gohil <hgohil@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/spi/spi.c | 15 +++++----------
include/linux/spi/spi.h | 3 +++
2 files changed, 8 insertions(+), 10 deletions(-)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -472,12 +472,6 @@ 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
@@ -581,7 +575,7 @@ int spi_add_device(struct spi_device *sp
* 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 = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
if (status) {
@@ -625,7 +619,7 @@ int spi_add_device(struct spi_device *sp
}
done:
- mutex_unlock(&spi_add_lock);
+ mutex_unlock(&ctlr->add_lock);
return status;
}
EXPORT_SYMBOL_GPL(spi_add_device);
@@ -2734,6 +2728,7 @@ int spi_register_controller(struct spi_c
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)
@@ -2879,7 +2874,7 @@ void spi_unregister_controller(struct sp
/* 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);
@@ -2910,7 +2905,7 @@ void spi_unregister_controller(struct sp
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);
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -528,6 +528,9 @@ struct spi_controller {
/* I/O mutex */
struct mutex io_mutex;
+ /* Used to avoid adding the same CS twice */
+ struct mutex add_lock;
+
/* lock and mutex for SPI bus locking */
spinlock_t bus_lock_spinlock;
struct mutex bus_lock_mutex;
