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Commit 85ba8f52 authored by Solomon Peachy's avatar Solomon Peachy Committed by John W. Linville
Browse files

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: default avatarSolomon Peachy <pizza@shaftnet.org>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent aec8e88c

drivers/net/wireless/cw1200/cw1200_spi.c

+9 −0
Original line number Diff line number Diff line
@@ -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,