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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 /include/linux/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 'include/linux/spi')
-rw-r--r--include/linux/spi/spi.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 8371bca13729..6b0b686f6f90 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;