Patch "cxgb4: fix BUG() on interrupt deallocating path of ULD" has been added to the 4.12-stable tree

This is a note to let you know that I've just added the patch titled

cxgb4: fix BUG() on interrupt deallocating path of ULD

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cxgb4-fix-bug-on-interrupt-deallocating-path-of-uld.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Guilherme G. Piccoli" <[email protected]>
Date: Mon, 10 Jul 2017 10:55:46 -0300
Subject: cxgb4: fix BUG() on interrupt deallocating path of ULD

From: "Guilherme G. Piccoli" <[email protected]>

[ Upstream commit 6a146f3a5894b751cef16feb3d7903e45e3c445c ]

Since the introduction of ULD (Upper-Layer Drivers), the MSI-X deallocating path changed in cxgb4: the driver frees the interrupts of ULD when unregistering it or on shutdown PCI handler.

Problem is that if a MSI-X is not freed before deallocated in the PCI layer, it will trigger a BUG() due to still "alive" interrupt being tentatively quiesced.

The below trace was observed when doing a simple unbind of Chelsio's adapter PCI function, like:
"echo 001e:80:00.4 > /sys/bus/pci/drivers/cxgb4/unbind"

Trace:

kernel BUG at drivers/pci/msi.c:352!

  Oops: Exception in kernel mode, sig: 5 [#1]
  ...
  NIP [c0000000005a5e60] free_msi_irqs+0xa0/0x250
  LR [c0000000005a5e50] free_msi_irqs+0x90/0x250
  Call Trace:
  [c0000000005a5e50] free_msi_irqs+0x90/0x250 (unreliable)
  [c0000000005a72c4] pci_disable_msix+0x124/0x180
  [d000000011e06708] disable_msi+0x88/0xb0 [cxgb4]
  [d000000011e06948] free_some_resources+0xa8/0x160 [cxgb4]
  [d000000011e06d60] remove_one+0x170/0x3c0 [cxgb4]
  [c00000000058a910] pci_device_remove+0x70/0x110
  [c00000000064ef04] device_release_driver_internal+0x1f4/0x2c0
  ...

This patch fixes the issue by refactoring the shutdown path of ULD on cxgb4 driver, by properly freeing and disabling interrupts on PCI remove handler too.

---
 drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c |   16 ++++++---
 drivers/net/ethernet/chelsio/cxgb4/cxgb4_uld.c  |   42 ++++++++++++++----------
 2 files changed, 36 insertions(+), 22 deletions(-)

@@ -2055,12 +2055,12 @@ static void detach_ulds(struct adapter *
 
 	mutex_lock(&uld_mutex);
 	list_del(&adap->list_node);
+
 	for (i = 0; i < CXGB4_ULD_MAX; i++)
-		if (adap->uld && adap->uld[i].handle) {
+		if (adap->uld && adap->uld[i].handle)
 			adap->uld[i].state_change(adap->uld[i].handle,
 					     CXGB4_STATE_DETACH);
-			adap->uld[i].handle = NULL;
-		}
+
 	if (netevent_registered && list_empty(&adapter_list)) {
 		unregister_netevent_notifier(&cxgb4_netevent_nb);
 		netevent_registered = false;

@@ -5086,8 +5086,10 @@ static void remove_one(struct pci_dev *p
 		 */
 		destroy_workqueue(adapter->workq);
 
-		if (is_uld(adapter))
+		if (is_uld(adapter)) {
 			detach_ulds(adapter);
+			t4_uld_clean_up(adapter);
+		}
 
 		disable_interrupts(adapter);
 

@@ -5164,7 +5166,11 @@ static void shutdown_one(struct pci_dev
 			if (adapter->port[i]->reg_state == NETREG_REGISTERED)
 				cxgb_close(adapter->port[i]);
 
-		t4_uld_clean_up(adapter);
+		if (is_uld(adapter)) {
+			detach_ulds(adapter);
+			t4_uld_clean_up(adapter);
+		}
+
 		disable_interrupts(adapter);
 		disable_msi(adapter);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/cxgb4-fix-bug-on-interrupt-deallocating-path-of-uld.patch