diff options
| author |   Solomon Peachy <pizza@shaftnet.org> | 2013-08-27 20:29:47 -0400 |
|---|---|---|
| committer |   John W. Linville <linville@tuxdriver.com> | 2013-09-09 14:40:54 -0400 |
| commit | 85ba8f529c57ac6e2fca9be0d9e17920a1afb2e8 (patch) | |
| tree | bb22dd1b9f6e5b442d3c6c2bad87476baa4b9e0f /drivers/net/wireless/cw1200 | |
| parent | cw1200: Don't perform SPI transfers in interrupt context (diff) | |
| download | linux-dev-85ba8f529c57ac6e2fca9be0d9e17920a1afb2e8.tar.xz linux-dev-85ba8f529c57ac6e2fca9be0d9e17920a1afb2e8.zip | |
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>
Diffstat (limited to 'drivers/net/wireless/cw1200')
| -rw-r--r-- | drivers/net/wireless/cw1200/cw1200_spi.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/net/wireless/cw1200/cw1200_spi.c b/drivers/net/wireless/cw1200/cw1200_spi.c index c31580ba883b..f5e6b489ed32 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, |