openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

cw1200: Prevent a lock-related hang in the cw1200_spi driver 

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@shaftnet.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Solomon Peachy 2013-08-27 20:29:47 -04:00 committed by John W. Linville
parent aec8e88c94
commit 85ba8f529c
1 changed files with 9 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/net/wireless/cw1200/cw1200_spi.c
View File

@ -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,