From 6098475d4cb48d821bdf453c61118c56e26294f0 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Fri, 8 Oct 2021 14:31:57 +0100 Subject: [PATCH] spi: Fix deadlock when adding SPI controllers on SPI buses MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Mark Brown --- drivers/spi/spi.c | 17 ++++++----------- include/linux/spi/spi.h | 3 +++ 2 files changed, 9 insertions(+), 11 deletions(-) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index aea037c..412a105 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); diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 8371bca..6b0b686 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -531,6 +531,9 @@ 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; -- 2.7.4