[ 69/71] cw1200: Prevent a lock-related hang in the cw1200_spi driver
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2013-09-29 19:33:37
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3.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Solomon Peachy <redacted> commit 85ba8f529c57ac6e2fca9be0d9e17920a1afb2e8 upstream. 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 <redacted> Signed-off-by: John W. Linville <redacted> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/net/wireless/cw1200/cw1200_spi.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- 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; };
@@ -197,8 +198,11 @@ static void cw1200_spi_lock(struct hwbus { 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);
@@ -211,6 +215,7 @@ static void cw1200_spi_lock(struct hwbus set_current_state(TASK_RUNNING); self->claimed = 1; spin_unlock_irqrestore(&self->lock, flags); + remove_wait_queue(&self->wq, &wait); return; }
@@ -222,6 +227,8 @@ static void cw1200_spi_unlock(struct hwb spin_lock_irqsave(&self->lock, flags); self->claimed = 0; spin_unlock_irqrestore(&self->lock, flags); + wake_up(&self->wq); + return; }
@@ -400,6 +407,8 @@ static int cw1200_spi_probe(struct spi_d spi_set_drvdata(func, self); + init_waitqueue_head(&self->wq); + status = cw1200_spi_irq_subscribe(self); status = cw1200_core_probe(&cw1200_spi_hwbus_ops,