PCI: fix BUG_ON triggered by logical PCIe root port removal

This problem happened when removing PCIe root port using PCI logical
hotplug operation.

The immediate cause of this problem is that the pointer to invalid
data structure is passed to pcie_update_aspm_capable() by
pcie_aspm_exit_link_state(). When pcie_aspm_exit_link_state() received
a pointer to root port link, it unconfigures the root port link and
frees its data structure at first. At this point, there are not links
to configure under the root port and the data structure for root port
link is already freed. So pcie_aspm_exit_link_state() must not call
pcie_update_aspm_capable() and pcie_config_aspm_path().

This patch fixes the problem by changing pcie_aspm_exit_link_state()
not to call pcie_update_aspm_capable() and pcie_config_aspm_path() if
the specified link is root port link.

------------[ cut here ]------------
kernel BUG at drivers/pci/pcie/aspm.c:606!
invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC
last sysfs file: /sys/devices/pci0000:40/0000:40:13.0/remove
CPU 1
Modules linked in: shpchp
Pid: 9345, comm: sysfsd Not tainted 2.6.32-rc5 #98 ProLiant DL785 G6
RIP: 0010:[<ffffffff811df69b>]  [<ffffffff811df69b>] pcie_update_aspm_capable+0x15/0xbe
RSP: 0018:ffff88082a2f5ca0  EFLAGS: 00010202
RAX: 0000000000000e77 RBX: ffff88182cc3e000 RCX: ffff88082a33d006
RDX: 0000000000000001 RSI: ffffffff811dff4a RDI: ffff88182cc3e000
RBP: ffff88082a2f5cc0 R08: ffff88182cc3e000 R09: 0000000000000000
R10: ffff88182fc00180 R11: ffff88182fc00198 R12: ffff88182cc3e000
R13: 0000000000000000 R14: ffff88182cc3e000 R15: ffff88082a2f5e20
FS:  00007f259a64b6f0(0000) GS:ffff880864600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: 00007feb53f73da0 CR3: 000000102cc94000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process sysfsd (pid: 9345, threadinfo ffff88082a2f4000, task ffff88082a33cf00)
Stack:
 ffff88182cc3e000 ffff88182cc3e000 0000000000000000 ffff88082a33cf00
<0> ffff88082a2f5cf0 ffffffff811dff52 ffff88082a2f5cf0 ffff88082c525168
<0> ffff88402c9fd2f8 ffff88402c9fd2f8 ffff88082a2f5d20 ffffffff811d7db2
Call Trace:
 [<ffffffff811dff52>] pcie_aspm_exit_link_state+0xf5/0x11e
 [<ffffffff811d7db2>] pci_stop_bus_device+0x76/0x7e
 [<ffffffff811d7d67>] pci_stop_bus_device+0x2b/0x7e
 [<ffffffff811d7e4f>] pci_remove_bus_device+0x15/0xb9
 [<ffffffff811dcb8c>] remove_callback+0x29/0x3a
 [<ffffffff81135aeb>] sysfs_schedule_callback_work+0x15/0x6d
 [<ffffffff81072790>] worker_thread+0x19d/0x298
 [<ffffffff8107273b>] ? worker_thread+0x148/0x298
 [<ffffffff81135ad6>] ? sysfs_schedule_callback_work+0x0/0x6d
 [<ffffffff810765c0>] ? autoremove_wake_function+0x0/0x38
 [<ffffffff810725f3>] ? worker_thread+0x0/0x298
 [<ffffffff8107629e>] kthread+0x7d/0x85
 [<ffffffff8102eafa>] child_rip+0xa/0x20
 [<ffffffff8102e4bc>] ? restore_args+0x0/0x30
 [<ffffffff81076221>] ? kthread+0x0/0x85
 [<ffffffff8102eaf0>] ? child_rip+0x0/0x20
Code: 89 e5 8a 50 48 31 c0 c0 ea 03 83 e2 07 e8 b2 de fe ff c9 48 98 c3 55 48 89 e5 41 56 49 89 fe 41 55 41 54 53 48 83 7f 10 00 74 04 <0f> 0b eb fe 48 8b 05 da 7d 63 00 4c 8d 60 e8 4c 89 e1 eb 24 4c
RIP  [<ffffffff811df69b>] pcie_update_aspm_capable+0x15/0xbe
 RSP <ffff88082a2f5ca0>
---[ end trace 6ae0f65bdeab8555 ]---

Reported-by: Alex Chiang <achiang@hp.com>
Tested-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pcie/aspm.c

@@ -657,8 +657,10 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 	free_link_state(link);
 
 	/* Recheck latencies and configure upstream links */
+	if (parent_link) {
 		pcie_update_aspm_capable(root);
 		pcie_config_aspm_path(parent_link);
+	}
 out:
 	mutex_unlock(&aspm_lock);
 	up_read(&pci_bus_sem);