rt2x00: Fix PCI interrupt processing race on SMP systems

When toggle_irq is called for PCI devices to disable device interrupts
it used tasklet_disable to wait for a possibly running tasklet to finish.
However, on SMP systems the tasklet might still be scheduled on another CPU.
Instead, use tasklet_kill to ensure that all scheduled tasklets are finished
before returning from toggle_irq.

Furthermore, it was possible that a tasklet reenabled its interrupt even
though interrupts have been disabled already. Fix this by checking the
DEVICE_STATE_ENABLED_RADIO flag before reenabling single interrupts
during tasklet processing.

While at it also enable/kill the TBTT and PRETBTT tasklets in the
toggle_irq callback and only use tasklet_kill in stop_queue to wait
for a currently scheduled beacon update before returning.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 19 insertions, 27 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2800pci.c b/drivers/net/wireless/rt2x00/rt2800pci.c
index ebc17ad61dec..cabf249aa55b 100644
--- a/drivers/net/wireless/rt2x00/rt2800pci.c
+++ b/drivers/net/wireless/rt2x00/rt2800pci.c
@@ -200,13 +200,6 @@ static void rt2800pci_start_queue(struct data_queue *queue)
 		rt2x00pci_register_write(rt2x00dev, MAC_SYS_CTRL, reg);
 		break;
 	case QID_BEACON:
-		/*
-		 * Allow beacon tasklets to be scheduled for periodic
-		 * beacon updates.
-		 */
-		tasklet_enable(&rt2x00dev->tbtt_tasklet);
-		tasklet_enable(&rt2x00dev->pretbtt_tasklet);
-
 		rt2x00pci_register_read(rt2x00dev, BCN_TIME_CFG, &reg);
 		rt2x00_set_field32(&reg, BCN_TIME_CFG_TSF_TICKING, 1);
 		rt2x00_set_field32(&reg, BCN_TIME_CFG_TBTT_ENABLE, 1);
@@ -269,10 +262,13 @@ static void rt2800pci_stop_queue(struct data_queue *queue)
 		rt2x00pci_register_write(rt2x00dev, INT_TIMER_EN, reg);
 
 		/*
-		 * Wait for tbtt tasklets to finish.
+		 * Wait for current invocation to finish. The tasklet
+		 * won't be scheduled anymore afterwards since we disabled
+		 * the TBTT and PRE TBTT timer.
 		 */
-		tasklet_disable(&rt2x00dev->tbtt_tasklet);
-		tasklet_disable(&rt2x00dev->pretbtt_tasklet);
+		tasklet_kill(&rt2x00dev->tbtt_tasklet);
+		tasklet_kill(&rt2x00dev->pretbtt_tasklet);
+
 		break;
 	default:
 		break;
@@ -437,14 +433,6 @@ static void rt2800pci_toggle_irq(struct rt2x00_dev *rt2x00dev,
 	if (state == STATE_RADIO_IRQ_ON) {
 		rt2x00pci_register_read(rt2x00dev, INT_SOURCE_CSR, &reg);
 		rt2x00pci_register_write(rt2x00dev, INT_SOURCE_CSR, reg);
-
-		/*
-		 * Enable tasklets. The beacon related tasklets are
-		 * enabled when the beacon queue is started.
-		 */
-		tasklet_enable(&rt2x00dev->txstatus_tasklet);
-		tasklet_enable(&rt2x00dev->rxdone_tasklet);
-		tasklet_enable(&rt2x00dev->autowake_tasklet);
 	}
 
 	spin_lock_irqsave(&rt2x00dev->irqmask_lock, flags);
@@ -472,12 +460,13 @@ static void rt2800pci_toggle_irq(struct rt2x00_dev *rt2x00dev,
 
 	if (state == STATE_RADIO_IRQ_OFF) {
 		/*
-		 * Ensure that all tasklets are finished before
-		 * disabling the interrupts.
+		 * Wait for possibly running tasklets to finish.
 		 */
-		tasklet_disable(&rt2x00dev->txstatus_tasklet);
-		tasklet_disable(&rt2x00dev->rxdone_tasklet);
-		tasklet_disable(&rt2x00dev->autowake_tasklet);
+		tasklet_kill(&rt2x00dev->txstatus_tasklet);
+		tasklet_kill(&rt2x00dev->rxdone_tasklet);
+		tasklet_kill(&rt2x00dev->autowake_tasklet);
+		tasklet_kill(&rt2x00dev->tbtt_tasklet);
+		tasklet_kill(&rt2x00dev->pretbtt_tasklet);
 	}
 }
 
@@ -813,14 +802,16 @@ static void rt2800pci_pretbtt_tasklet(unsigned long data)
 {
 	struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
 	rt2x00lib_pretbtt(rt2x00dev);
-	rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_PRE_TBTT);
+	if (test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
+		rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_PRE_TBTT);
 }
 
 static void rt2800pci_tbtt_tasklet(unsigned long data)
 {
 	struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
 	rt2x00lib_beacondone(rt2x00dev);
-	rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_TBTT);
+	if (test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
+		rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_TBTT);
 }
 
 static void rt2800pci_rxdone_tasklet(unsigned long data)
@@ -828,7 +819,7 @@ static void rt2800pci_rxdone_tasklet(unsigned long data)
 	struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
 	if (rt2x00pci_rxdone(rt2x00dev))
 		tasklet_schedule(&rt2x00dev->rxdone_tasklet);
-	else
+	else if (test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 		rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_RX_DONE);
 }
 
@@ -836,7 +827,8 @@ static void rt2800pci_autowake_tasklet(unsigned long data)
 {
 	struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
 	rt2800pci_wakeup(rt2x00dev);
-	rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_AUTO_WAKEUP);
+	if (test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
+		rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_AUTO_WAKEUP);
 }
 
 static void rt2800pci_txstatus_interrupt(struct rt2x00_dev *rt2x00dev)