[PATCH] pci: aer: wait till the workqueue completes before free memory

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

I start a binary which should flash the FPGA and re-enumare the PCI-BUS
and find a new device. It works most of the time. With SLUB debug it
crashes on each iteration with something like this (compressed output):

| pcieport 0000:00:00.0: AER: Multiple Corrected error received: id=0000
| Unable to handle kernel paging request for data at address 0x27ef9e3e
| Faulting instruction address: 0x602f5328
| Oops: Kernel access of bad area, sig: 11 [#1]
| Workqueue: events aer_isr
| GPR24: dd6aa000 6b6b6b6b 605f8378 605f8360 d99b12c0 604fc674 606b1704 d99b12c0
| NIP [602f5328] pci_walk_bus+0xd4/0x104

Register 25 has the user-after magic. As it turns out, the old PCIe
device is leaving, generates an error before it left, aer_irq() is fired,
it schedules a work item. What happens now is that free_irq() is
invoked, all resources are gone *before* the aes_isr() work item is
completed.
So to fix this, I flush the workqueue to ensure that there is no more
work pending.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
Bjorn, this could deserve a stable tag. However it seems to have been
like that even in v2.6.20.

 drivers/pci/pcie/aer/aerdrv.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/aer/aerdrv.c b/drivers/pci/pcie/aer/aerdrv.c
index 0bf82a20a0fb..7acd27348098 100644
--- a/drivers/pci/pcie/aer/aerdrv.c
+++ b/drivers/pci/pcie/aer/aerdrv.c
@@ -282,8 +282,10 @@ static void aer_remove(struct pcie_device *dev)
 
 	if (rpc) {
 		/* If register interrupt service, it must be free. */
-		if (rpc->isr)
+		if (rpc->isr) {
 			free_irq(dev->irq, dev);
+			flush_work(&rpc->dpc_handler);
+		}
 
 		wait_event(rpc->wait_release, rpc->prod_idx == rpc->cons_idx);
 
-- 
2.6.4