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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 556351f14e ("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: 556351f14e ("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>
This commit is contained in:
Jon Hunter 2016-03-08 12:28:20 +00:00 committed by Mark Brown
parent 628269704f
commit 49023d2e4e
1 changed files with 17 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/spi/spi.c
View File

@ -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)
}
}
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;
}
@ -1172,20 +1175,22 @@ 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;
}
out:
if (!bus_locked)
mutex_unlock(&master->bus_lock_mutex);
/* Prod the scheduler in case transfer_one() was busy waiting */
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);