The cw1200_spi driver tries to mirror the cw1200_sdio driver's lock
API, which relies on sdio_claim_host/sdio_release_host to serialize
hardware operations across multiple threads.
Unfortunately the implementation was flawed, as it lacked a way to wake
up the lock requestor when there was contention, often resulting in a
hang.
This problem was uncovered while trying to fix the
spi-transfers-in-interrupt-context BUG() corrected in the previous
patch. Many thanks to Dave Sizeburns for his assistance in fixing this.
Signed-off-by: Solomon Peachy <pizza@xxxxxxxxxxxx>
---
Please consider this for 3.11-rc; without this patch SPI users are all
but guaranteed to deadlock while running this driver.
drivers/net/wireless/cw1200/cw1200_spi.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/net/wireless/cw1200/cw1200_spi.c b/drivers/net/wireless/cw1200/cw1200_spi.c
index c31580b..f5e6b48 100644
--- a/drivers/net/wireless/cw1200/cw1200_spi.c
+++ b/drivers/net/wireless/cw1200/cw1200_spi.c
@@ -40,6 +40,7 @@ struct hwbus_priv {
struct cw1200_common *core;
const struct cw1200_platform_data_spi *pdata;
spinlock_t lock; /* Serialize all bus operations */
+ wait_queue_head_t wq;
int claimed;
int irq_disabled;
};
@@ -198,8 +199,11 @@ static void cw1200_spi_lock(struct hwbus_priv *self)
{
unsigned long flags;
+ DECLARE_WAITQUEUE(wait, current);
+
might_sleep();
+ add_wait_queue(&self->wq, &wait);
spin_lock_irqsave(&self->lock, flags);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
@@ -212,6 +216,7 @@ static void cw1200_spi_lock(struct hwbus_priv *self)
set_current_state(TASK_RUNNING);
self->claimed = 1;
spin_unlock_irqrestore(&self->lock, flags);
+ remove_wait_queue(&self->wq, &wait);
return;
}
@@ -223,6 +228,8 @@ static void cw1200_spi_unlock(struct hwbus_priv *self)
spin_lock_irqsave(&self->lock, flags);
self->claimed = 0;
spin_unlock_irqrestore(&self->lock, flags);
+ wake_up(&self->wq);
+
return;
}
@@ -413,6 +420,8 @@ static int cw1200_spi_probe(struct spi_device *func)
spi_set_drvdata(func, self);
+ init_waitqueue_head(&self->wq);
+
status = cw1200_spi_irq_subscribe(self);
status = cw1200_core_probe(&cw1200_spi_hwbus_ops,
--
1.8.3.1
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