PCI, x86: clear initial value for root info resources

Found one system one root bus hot remove get panic.
Panic happens when try to release hostbridge resource.

It turns out that resource get reject during put into resource tree
because of conflicts.
Also that resource parent pointer have random value.

That invalid value cause it pass through check __release_pci_root_info
and panic in release_resource.

Try to use kzalloc instead.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: x86@kernel.org

---
 arch/x86/pci/acpi.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

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On Wed, Sep 19, 2012 at 10:49:00AM -0700, Yinghai Lu wrote:
> Found one system one root bus hot remove get panic.

Boy, this is mangled.

Can you include the name of the system? Perhaps you can
rephrase this to say:

"On XYZ removing the root bus (through ACPI unplug) causes
a panic."

> Panic happens when try to release hostbridge resource.

Can you include the stack trace?
> 
> It turns out that resource get reject during put into resource tree
> because of conflicts.

Come again? Are you saying:

"The reason for this is that the resources was never initialized
properly because of .. (what type of conflict?)"?

> Also that resource parent pointer have random value.
> 
> That invalid value cause it pass through check __release_pci_root_info
> and panic in release_resource.
> 
> Try to use kzalloc instead.

It is not just try, it _is_ using that now.

> 
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> Cc: x86@kernel.org
> 
> ---
>  arch/x86/pci/acpi.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> Index: linux-2.6/arch/x86/pci/acpi.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/pci/acpi.c
> +++ linux-2.6/arch/x86/pci/acpi.c
> @@ -305,7 +305,6 @@ setup_resource(struct acpi_resource *acp
>  	res->flags = flags;
>  	res->start = start;
>  	res->end = end;
> -	res->child = NULL;
>  
>  	if (!pci_use_crs) {
>  		dev_printk(KERN_DEBUG, &info->bridge->dev,
> @@ -434,7 +433,7 @@ probe_pci_root_info(struct pci_root_info
>  
>  	size = sizeof(*info->res) * info->res_num;
>  	info->res_num = 0;
> -	info->res = kmalloc(size, GFP_KERNEL);
> +	info->res = kzalloc(size, GFP_KERNEL);
>  	if (!info->res)
>  		return;
>  
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On Fri, Sep 21, 2012 at 11:27:00AM -0700, Yinghai Lu wrote:
> On Fri, Sep 21, 2012 at 9:50 AM, Konrad Rzeszutek Wilk
> <konrad@kernel.org> wrote:
> > On Wed, Sep 19, 2012 at 10:49:00AM -0700, Yinghai Lu wrote:
> >
> > Can you include the stack trace?
> 
> [  414.997281] pci_bus 0000:00: freeing pci_bus info
> [  415.017221]  pci0000:00: freeing pci_host_bridge info
> [  415.017468] general protection fault: 0000 [#1] SMP
> [  415.036758] Modules linked in:
> [  415.036959] CPU 0
> [  415.037051] Pid: 4, comm: kworker/0:0 Not tainted
> 3.6.0-rc6-yh-03463-gbcab6f1-dirty #303 Oracle Corporation  Sun Fire
> X4800 M2 /
> [  415.056989] RIP: 0010:[<ffffffff81075218>]  [<ffffffff81075218>]
> __release_resource+0x11/0x3e
> [  415.076854] RSP: 0018:ffff883f4cea39f0  EFLAGS: 00010206
> [  415.077112] RAX: 0d00000000000030 RBX: ffff897ea6cd4070 RCX: 8c6318c6318c6320
> [  415.097000] RDX: ffff883f9d60e190 RSI: ffffffff8265f228 RDI: ffff897ea6cd4070
> [  415.116627] RBP: ffff883f4cea39f0 R08: 0000000000000005 R09: ffffffff810755de
> [  415.116953] R10: ffffffff81e2e7df R11: 0000000000000000 R12: 0000000000000002
> [  415.136790] R13: ffff897ea6d18600 R14: ffffffff826f18c0 R15: ffff883f9d60d800
> [  415.156541] FS:  0000000000000000(0000) GS:ffff883f9d600000(0000)
> knlGS:0000000000000000
> [  415.156953] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [  415.176622] CR2: 0000000000619718 CR3: 000000000263f000 CR4: 00000000000007f0
> [  415.196401] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  415.196761] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [  415.216702] Process kworker/0:0 (pid: 4, threadinfo
> ffff883f4cea2000, task ffff883f4cea8000)
> [  415.236370] Stack:
> [  415.236475]  ffff883f4cea3a20 ffffffff810755e6 ffff883f4cea3a60
> ffff883f00000000
> [  415.236866]  ffffffff824884ad ffff88fea6ce2440 ffff883f4cea3a40
> ffffffff81c2cfc5
> [  415.256682]  ffff88bf4a1ec800 ffff88bf4a1ec800 ffff883f4cea3a50
> ffffffff81c2d023
> [  415.276452] Call Trace:
> [  415.276611]  [<ffffffff810755e6>] release_resource+0x25/0x3e
> [  415.296206]  [<ffffffff81c2cfc5>] __release_pci_root_info+0x35/0x7e
> [  415.296556]  [<ffffffff81c2d023>] release_pci_root_info+0x15/0x1a
> [  415.316249]  [<ffffffff813f568a>] pci_release_bus_bridge_dev+0x37/0x4f
> [  415.316581]  [<ffffffff815c04d8>] device_release+0x93/0xcb
> [  415.336365]  [<ffffffff813d5888>] kobject_release+0x51/0x67
> [  415.336666]  [<ffffffff813d579a>] kobject_put+0x4a/0x4e
> [  415.361466]  [<ffffffff815c026a>] put_device+0x17/0x19
> [  415.361734]  [<ffffffff813f75b2>] pci_remove_root_bus+0x5a/0x64
> [  415.376188]  [<ffffffff81437dd8>] acpi_pci_root_remove+0xeb/0x114
> [  415.376509]  [<ffffffff81434c13>] acpi_device_remove+0x86/0xa5
> [  415.396230]  [<ffffffff815c33b6>] __device_release_driver+0x86/0xdc
> [  415.396551]  [<ffffffff815c3431>] device_release_driver+0x25/0x32
> [  415.416198]  [<ffffffff8143658b>] acpi_bus_trim+0x86/0x110
> [  415.416473]  [<ffffffff81439ae1>] handle_root_bridge_removal+0x4f/0x118
> [  415.436227]  [<ffffffff81439c8b>] _handle_hotplug_event_root+0xe1/0x121
> [  415.455957]  [<ffffffff81085515>] process_one_work+0x28a/0x453
> [  415.456228]  [<ffffffff81085480>] ? process_one_work+0x1f5/0x453
> [  415.475980]  [<ffffffff81439baa>] ? handle_root_bridge_removal+0x118/0x118
> [  415.476311]  [<ffffffff81085bd1>] worker_thread+0x12a/0x201
> [  415.495995]  [<ffffffff81085aa7>] ? manage_workers+0xed/0xed
> [  415.496301]  [<ffffffff8108b93a>] kthread+0xe7/0xef
> [  415.515957]  [<ffffffff81e2ef03>] ? _raw_spin_unlock_irq+0x2e/0x33
> [  415.516257]  [<ffffffff81e372e4>] kernel_thread_helper+0x4/0x10
> [  415.535926]  [<ffffffff81e2f259>] ? retint_restore_args+0xe/0xe
> [  415.536242]  [<ffffffff8108b853>] ? __init_kthread_worker+0x5a/0x5a
> [  415.555959]  [<ffffffff81e372e0>] ? gs_change+0xb/0xb
> [  415.556209] Code: 48 89 31 48 89 46 20 31 c0 eb 0d 48 39 7a 08 48
> 8d 4a 28 72 da 48 89 d0 5d c3 66 66 66 66 90 48 8b 47 20 55 48 89 e5
> 48 83 c0 30 <48> 8b 10 48 85 d2 74 1e 48 39 fa 75 13 48 8b 57 28 48 89
> 10 48
> [  415.596509] RIP  [<ffffffff81075218>] __release_resource+0x11/0x3e
> [  415.615741]  RSP <ffff883f4cea39f0>
> [  415.616020] ---[ end trace 8bcbc1bea9c3e0bc ]---
> 
> whole log is attached.

I meant it (and a filtered with just the valid lines in it) in terms of the patch commit description.
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