wimax/i2400m: fix oops caused by race condition when exiting USB kthreads
Current i2400m USB code had to threads (one for processing RX, one for
TX). When calling i2400m_{tx,rx}_release(), it would crash if the
thread had exited already due to an error.
So changed the code to have the thread fill in/out
i2400mu->{tx,rx}_kthread under a spinlock; then the _release()
function will call kthread_stop() only if {rx,tx}_kthread is still
set.
Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
diff --git a/drivers/net/wimax/i2400m/usb-tx.c b/drivers/net/wimax/i2400m/usb-tx.c
index 90dfff1..a3c46e9 100644
--- a/drivers/net/wimax/i2400m/usb-tx.c
+++ b/drivers/net/wimax/i2400m/usb-tx.c
@@ -161,9 +161,15 @@
struct device *dev = &i2400mu->usb_iface->dev;
struct i2400m_msg_hdr *tx_msg;
size_t tx_msg_size;
+ unsigned long flags;
d_fnstart(4, dev, "(i2400mu %p)\n", i2400mu);
+ spin_lock_irqsave(&i2400m->tx_lock, flags);
+ BUG_ON(i2400mu->tx_kthread != NULL);
+ i2400mu->tx_kthread = current;
+ spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+
while (1) {
d_printf(2, dev, "TX: waiting for messages\n");
tx_msg = NULL;
@@ -183,6 +189,11 @@
if (result < 0)
break;
}
+
+ spin_lock_irqsave(&i2400m->tx_lock, flags);
+ i2400mu->tx_kthread = NULL;
+ spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+
d_fnend(4, dev, "(i2400mu %p) = %d\n", i2400mu, result);
return result;
}
@@ -213,11 +224,13 @@
struct i2400m *i2400m = &i2400mu->i2400m;
struct device *dev = &i2400mu->usb_iface->dev;
struct wimax_dev *wimax_dev = &i2400m->wimax_dev;
+ struct task_struct *kthread;
- i2400mu->tx_kthread = kthread_run(i2400mu_txd, i2400mu, "%s-tx",
- wimax_dev->name);
- if (IS_ERR(i2400mu->tx_kthread)) {
- result = PTR_ERR(i2400mu->tx_kthread);
+ kthread = kthread_run(i2400mu_txd, i2400mu, "%s-tx",
+ wimax_dev->name);
+ /* the kthread function sets i2400mu->tx_thread */
+ if (IS_ERR(kthread)) {
+ result = PTR_ERR(kthread);
dev_err(dev, "TX: cannot start thread: %d\n", result);
}
return result;
@@ -225,5 +238,17 @@
void i2400mu_tx_release(struct i2400mu *i2400mu)
{
- kthread_stop(i2400mu->tx_kthread);
+ unsigned long flags;
+ struct i2400m *i2400m = &i2400mu->i2400m;
+ struct device *dev = i2400m_dev(i2400m);
+ struct task_struct *kthread;
+
+ spin_lock_irqsave(&i2400m->tx_lock, flags);
+ kthread = i2400mu->tx_kthread;
+ i2400mu->tx_kthread = NULL;
+ spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+ if (kthread)
+ kthread_stop(kthread);
+ else
+ d_printf(1, dev, "TX: kthread had already exited\n");
}