commit 94dec6a2d20a26a779b63bb584e48db5fb0ddb53
author Ben Hutchings <bhutchings@solarflare.com> Tue Dec 07 19:24:45 2010 +0000
committer Ben Hutchings <bhutchings@solarflare.com> Tue Dec 07 19:30:19 2010 +0000
tree 3911c0883429411e27f22db1e34436d75fbb937b
parent 46bcf14f44d8f31ecfdc8b6708ec15a3b33316d9

sfc: Fix crash in legacy onterrupt handler during ring reallocation

If we are using a legacy interrupt, our IRQ may be shared and our
interrupt handler may be called even though interrupts are disabled on
the NIC. When we change ring sizes, we reallocate the event queue and
the interrupt handler may use an invalid pointer when called for
another device's interrupt.

Maintain a legacy_irq_enabled flag and test that at the top of the
interrupt handler.  Note that this problem results from the need to
work around broken INT_ISR0 reads, and does not affect the legacy
interrupt handler for Falcon A1.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/sfc/efx.c

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 05df20e..d06cb74 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -335,8 +335,10 @@
 
 	/* Disable interrupts and wait for ISRs to complete */
 	efx_nic_disable_interrupts(efx);
-	if (efx->legacy_irq)
+	if (efx->legacy_irq) {
 		synchronize_irq(efx->legacy_irq);
+		efx->legacy_irq_enabled = false;
+	}
 	if (channel->irq)
 		synchronize_irq(channel->irq);
 
@@ -351,6 +353,8 @@
 	efx_channel_processed(channel);
 
 	napi_enable(&channel->napi_str);
+	if (efx->legacy_irq)
+		efx->legacy_irq_enabled = true;
 	efx_nic_enable_interrupts(efx);
 }
 
@@ -1400,6 +1404,8 @@
 		efx_start_channel(channel);
 	}
 
+	if (efx->legacy_irq)
+		efx->legacy_irq_enabled = true;
 	efx_nic_enable_interrupts(efx);
 
 	/* Switch to event based MCDI completions after enabling interrupts.
@@ -1460,8 +1466,10 @@
 
 	/* Disable interrupts and wait for ISR to complete */
 	efx_nic_disable_interrupts(efx);
-	if (efx->legacy_irq)
+	if (efx->legacy_irq) {
 		synchronize_irq(efx->legacy_irq);
+		efx->legacy_irq_enabled = false;
+	}
 	efx_for_each_channel(channel, efx) {
 		if (channel->irq)
 			synchronize_irq(channel->irq);

drivers/net/sfc/net_driver.h

diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index 0a7e26d..b137c88 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -621,6 +621,7 @@
  * @pci_dev: The PCI device
  * @type: Controller type attributes
  * @legacy_irq: IRQ number
+ * @legacy_irq_enabled: Are IRQs enabled on NIC (INT_EN_KER register)?
  * @workqueue: Workqueue for port reconfigures and the HW monitor.
  *	Work items do not hold and must not acquire RTNL.
  * @workqueue_name: Name of workqueue
@@ -709,6 +710,7 @@
 	struct pci_dev *pci_dev;
 	const struct efx_nic_type *type;
 	int legacy_irq;
+	bool legacy_irq_enabled;
 	struct workqueue_struct *workqueue;
 	char workqueue_name[16];
 	struct work_struct reset_work;

drivers/net/sfc/nic.c

diff --git a/drivers/net/sfc/nic.c b/drivers/net/sfc/nic.c
index 41c36b9..67cb0c9 100644
--- a/drivers/net/sfc/nic.c
+++ b/drivers/net/sfc/nic.c
@@ -1418,6 +1418,12 @@
 	u32 queues;
 	int syserr;
 
+	/* Could this be ours?  If interrupts are disabled then the
+	 * channel state may not be valid.
+	 */
+	if (!efx->legacy_irq_enabled)
+		return result;
+
 	/* Read the ISR which also ACKs the interrupts */
 	efx_readd(efx, &reg, FR_BZ_INT_ISR0);
 	queues = EFX_EXTRACT_DWORD(reg, 0, 31);