diff options
author | Jon Hunter <jonathanh@nvidia.com> | 2016-03-08 15:28:20 +0300 |
---|---|---|
committer | Mark Brown <broonie@kernel.org> | 2016-03-09 05:31:39 +0300 |
commit | 49023d2e4ead0fc9e0896331037746b267d46ad4 (patch) | |
tree | 4550038559a27f6698a6702b3ee20c833a669f7c /drivers/spi/spi.c | |
parent | 628269704f19fcfc765499b7158effccfc79b6cf (diff) | |
download | linux-49023d2e4ead0fc9e0896331037746b267d46ad4.tar.xz |
spi: core: Fix deadlock when sending messages
The function __spi_pump_messages() is called by spi_pump_messages() and
__spi_sync(). The function __spi_sync() has an argument 'bus_locked'
that indicates if it is called with the SPI bus mutex held or not. If
'bus_locked' is false then __spi_sync() will acquire the mutex itself.
Commit 556351f14e74 ("spi: introduce accelerated read support for spi
flash devices") made a change to acquire the SPI bus mutex within
__spi_pump_messages(). However, this change did not check to see if the
mutex is already held. If __spi_sync() is called with the mutex held
(ie. 'bus_locked' is true), then a deadlock occurs when
__spi_pump_messages() is called.
Fix this deadlock by passing the 'bus_locked' state from __spi_sync() to
__spi_pump_messages() and only acquire the mutex if not already held. In
the case where __spi_pump_messages() is called from spi_pump_messages()
it is assumed that the mutex is not held and so call
__spi_pump_messages() with 'bus_locked' set to false. Finally, move the
unlocking of the mutex to the end of the __spi_pump_messages() function
to simplify the code and only call cond_resched() if there are no
errors.
Fixes: 556351f14e74 ("spi: introduce accelerated read support for spi flash devices")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi.c')
-rw-r--r-- | drivers/spi/spi.c | 29 |
1 files changed, 17 insertions, 12 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 0b2bbf144460..f565cc8901a6 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1047,6 +1047,7 @@ EXPORT_SYMBOL_GPL(spi_finalize_current_transfer); * __spi_pump_messages - function which processes spi message queue * @master: master to process queue for * @in_kthread: true if we are in the context of the message pump thread + * @bus_locked: true if the bus mutex is held when calling this function * * This function checks if there is any spi message in the queue that * needs processing and if so call out to the driver to initialize hardware @@ -1056,7 +1057,8 @@ EXPORT_SYMBOL_GPL(spi_finalize_current_transfer); * inside spi_sync(); the queue extraction handling at the top of the * function should deal with this safely. */ -static void __spi_pump_messages(struct spi_master *master, bool in_kthread) +static void __spi_pump_messages(struct spi_master *master, bool in_kthread, + bool bus_locked) { unsigned long flags; bool was_busy = false; @@ -1152,7 +1154,9 @@ static void __spi_pump_messages(struct spi_master *master, bool in_kthread) } } - mutex_lock(&master->bus_lock_mutex); + if (!bus_locked) + mutex_lock(&master->bus_lock_mutex); + trace_spi_message_start(master->cur_msg); if (master->prepare_message) { @@ -1162,8 +1166,7 @@ static void __spi_pump_messages(struct spi_master *master, bool in_kthread) "failed to prepare message: %d\n", ret); master->cur_msg->status = ret; spi_finalize_current_message(master); - mutex_unlock(&master->bus_lock_mutex); - return; + goto out; } master->cur_msg_prepared = true; } @@ -1172,21 +1175,23 @@ static void __spi_pump_messages(struct spi_master *master, bool in_kthread) if (ret) { master->cur_msg->status = ret; spi_finalize_current_message(master); - mutex_unlock(&master->bus_lock_mutex); - return; + goto out; } ret = master->transfer_one_message(master, master->cur_msg); if (ret) { dev_err(&master->dev, "failed to transfer one message from queue\n"); - mutex_unlock(&master->bus_lock_mutex); - return; + goto out; } - mutex_unlock(&master->bus_lock_mutex); + +out: + if (!bus_locked) + mutex_unlock(&master->bus_lock_mutex); /* Prod the scheduler in case transfer_one() was busy waiting */ - cond_resched(); + if (!ret) + cond_resched(); } /** @@ -1198,7 +1203,7 @@ static void spi_pump_messages(struct kthread_work *work) struct spi_master *master = container_of(work, struct spi_master, pump_messages); - __spi_pump_messages(master, true); + __spi_pump_messages(master, true, false); } static int spi_init_queue(struct spi_master *master) @@ -2462,7 +2467,7 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message, spi_sync_immediate); SPI_STATISTICS_INCREMENT_FIELD(&spi->statistics, spi_sync_immediate); - __spi_pump_messages(master, false); + __spi_pump_messages(master, false, bus_locked); } wait_for_completion(&done); |