Latest bk kernel does not properly free PCI IO & MEM allocations

[Prarit Bhargava <prarit@sgi.com>]

Hello all,

I noticed this in testing of a hotplug driver I've written for SGI Altix hardware.

If you cat /proc/iomem and check lspci after removing a device via hotplug:

[root@cranberry3 linux-2.6.9-hotplug]# lspci
01:01.0 Co-processor: Silicon Graphics, Inc. IOC4 I/O controller (rev 4f)
01:03.0 SCSI storage controller: QLogic Corp. ISP12160 Dual Channel Ultra3 SCSI Processor (rev 06)
01:04.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5701 Gigabit Ethernet (rev 15)
03:02.0 ATM network controller: FORE Systems Inc ForeRunnerHE ATM Adapter
04:01.0 SCSI storage controller: QLogic Corp. QLA2200 64-bit Fibre Channel Adapter (rev 05)
[root@cranberry3 linux-2.6.9-hotplug]# cat /proc/iomem 
c00004080c200000-c00004080c2fffff : 0000:01:01.0
c00004080f400000-c00004080f4fffff : 0000:03:02.0
c00004080fe00000-c00004080fe00fff : 0000:04:01.0
c00004080fe01000-c00004080fe01fff : 0000:04:02.0
  00220000-0023ffff : 0000:04:01.0

There are still allocations listed for device 04:02.0 even though it has been
removed from the system.

I tracked down the issue to the following:

When pci_remove_bus_device is called on the device in the slot (should be a safe 
thing to do) both the pci_driver remove function for a device and the function 
pci_free_resources are called.

In the case of the QLA2x00 driver, the driver's remove function calls
pci_release_regions.  This function releases the IO & MEM allocs for the pci
device and kfree's them.

As previously mentioned, pci_free_resources is called.  This function attempts 
to use and free IO & MEM allocs for the pci device.

This may (about 5% of the time) causes an oops, ie) this is a critical issue for anyone
using hotplug.

This raises the following question -- should a driver be cleaning up resources or should
PCI?

P.



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