lkml.org 
[lkml]   [2013]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[ 69/71] cw1200: Prevent a lock-related hang in the cw1200_spi driver
Date
3.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Solomon Peachy <pizza@shaftnet.org>

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 <pizza@shaftnet.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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,



\
 
 \ /
  Last update: 2013-09-29 22:21    [W:0.085 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site