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Subject: Re: [RESEND BUGFIX PATCH 1/3] PCI/AER: fix pci_ops return NULL when
 hotplug a pci bus which was doing aer error inject
From: Huang Ying <ying.huang@intel.com>
To: Yijing Wang <wangyijing@huawei.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Mauro Carvalho Chehab <mchehab@redhat.com>,
	PCI <linux-pci@vger.kernel.org>, Jiang Liu <liuj97@gmail.com>,
	Hanjun Guo <guohanjun@huawei.com>, linux-kernel@vger.kernel.org
Date: Mon, 27 Aug 2012 09:23:19 +0800
In-Reply-To: <5038A210.4030005@huawei.com>
References: <1344685946-8172-1-git-send-email-wangyijing@huawei.com>
	 <5038A210.4030005@huawei.com>
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On Sat, 2012-08-25 at 17:59 +0800, Yijing Wang wrote:
> When we inject aer errors to the target pci device by aer_inject module, the pci_ops of pci
> bus which the target device is on will be assign to pci_ops_aer.So if the target pci device
> is a bridge, once we hotplug the pci bus(child bus) which the target device bridges to, child
> bus's pci_ops will be assigned to pci_ops_aer too.Now every access to the child bus's device
> will result to system panic, because it return NULL pci_ops in pci_read_aer.
> This patch fix this.
> 
> CallTrace:
> bash[5908]: NaT consumption 17179869216 [1]
> Modules linked in: aer_inject cpufreq_conservative cpufreq_userspace cpufreq_pow
> ersave acpi_cpufreq binfmt_misc fuse nls_iso8859_1 loop ipmi_si(+) ipmi_devintf
> ipmi_msghandler dm_mod ppdev iTCO_wdt iTCO_vendor_support sg igb parport_pc i2c_
> i801 mptctl i2c_core serio_raw hid_generic lpc_ich mfd_core parport button conta
> iner usbhid hid uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif ext3 mbca
> che jbd fan processor ide_pci_generic ide_core ata_piix libata mptsas mptscsih m
> ptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon
> 
> Pid: 5908, CPU 9, comm:                 bash
> psr : 00001010085a2010 ifs : 800000000000048e ip  : [<a000000220b815b0>]    Not
> tainted (3.5.0-rc6yijing-repo)
> ip is at pci_read_aer+0x330/0x460 [aer_inject]
> unat: 0000000000000000 pfs : 000000000000048e rsc : 0000000000000003
> rnat: 0000000000000000 bsps: 0000000000000000 pr  : 65519aa6a6969aa5
> ldrs: 0000000000000000 ccv : ffffffff00000001 fpsr: 0009804c8a70033f
> csd : 0000000000000000 ssd : 0000000000000000
> b0  : a000000220b815b0 b6  : a000000220b81280 b7  : a0000001006d56a0
> f6  : 1003e0000000000000005 f7  : 1003e0000000000000028
> f8  : 1003e00000000000000c8 f9  : 1003e0000000000000005
> f10 : 1003e627ec1e2f4c0d8a7 f11 : 1003e0000000000000011
> r1  : a0000001014e63c0 r2  : 0000000000000738 r3  : 000000000000fffe
> r8  : 0000000000000736 r9  : 0000000000000042 r10 : e000001f08f4c898
> r11 : 0000000000000000 r12 : e000000f3dfcfdc0 r13 : e000000f3dfc0000
> r14 : 0000000000000738 r15 : 0000000000004000 r16 : a000000220b827c8
> r17 : a000000220b827b8 r18 : ffffffffffffff00 r19 : e000000f073b0110
> r20 : 0000000000000042 r21 : e000000f073b0114 r22 : 0000000000000000
> r23 : e000000f073b0118 r24 : a0000001009e0e49 r25 : 0000000000000001
> r26 : 0000000000007041 r27 : e000000f3dfcfde0 r28 : 0000000000000000
> r29 : e000000f3dfcfc08 r30 : a000000220b827c8 r31 : e000001f074d6000
> 
> Call Trace:
>  [<a000000100016500>] show_stack+0x80/0xa0
>                                 sp=e000000f3dfcf800 bsp=e000000f3dfc1758
>  [<a000000100016b60>] show_regs+0x640/0x920
>                                 sp=e000000f3dfcf9d0 bsp=e000000f3dfc1700
>  [<a000000100040770>] die+0x190/0x2c0
>                                 sp=e000000f3dfcf9e0 bsp=e000000f3dfc16c0
>  [<a0000001000408f0>] die_if_kernel+0x50/0x80
>                                 sp=e000000f3dfcf9e0 bsp=e000000f3dfc1690
>  [<a000000100903a90>] ia64_fault+0xf0/0x15e0
>                                 sp=e000000f3dfcf9e0 bsp=e000000f3dfc1640
>  [<a00000010000c0a0>] ia64_native_leave_kernel+0x0/0x270
>                                 sp=e000000f3dfcfbf0 bsp=e000000f3dfc1640
>  [<a000000220b815b0>] pci_read_aer+0x330/0x460 [aer_inject]
>                                 sp=e000000f3dfcfdc0 bsp=e000000f3dfc15c8
>  [<a0000001004ace00>] pci_bus_read_config_dword+0xe0/0x140
>                                 sp=e000000f3dfcfdc0 bsp=e000000f3dfc1580
>  [<a0000001004b0c10>] pci_bus_read_dev_vendor_id+0x50/0x200
>                                 sp=e000000f3dfcfdd0 bsp=e000000f3dfc1530
>  [<a0000001008d3d10>] pci_scan_single_device+0x90/0x200
>                                 sp=e000000f3dfcfdd0 bsp=e000000f3dfc14f8
>  [<a0000001004b24b0>] pci_scan_slot+0xb0/0x320
>                                 sp=e000000f3dfcfde0 bsp=e000000f3dfc14a8
>  [<a0000001008d9e90>] pci_scan_child_bus+0x90/0x2e0
>                                 sp=e000000f3dfcfde0 bsp=e000000f3dfc1468
>  [<a0000001008d9580>] pci_scan_bridge+0x540/0xdc0
>                                 sp=e000000f3dfcfde0 bsp=e000000f3dfc13d0
>  [<a0000001008da0b0>] pci_scan_child_bus+0x2b0/0x2e0
>                                 sp=e000000f3dfcfe00 bsp=e000000f3dfc1390
>  [<a0000001008d5bd0>] pci_rescan_bus+0x50/0x220
>                                 sp=e000000f3dfcfe00 bsp=e000000f3dfc1358
>  [<a0000001004c2ab0>] bus_rescan_store+0xf0/0x160
>                                 sp=e000000f3dfcfe10 bsp=e000000f3dfc1328
>  [<a0000001006110b0>] bus_attr_store+0x70/0xa0
>                                 sp=e000000f3dfcfe20 bsp=e000000f3dfc12f0
>  [<a000000100343b00>] sysfs_write_file+0x240/0x340
>                                 sp=e000000f3dfcfe20 bsp=e000000f3dfc1298
>  [<a00000010025e230>] vfs_write+0x1b0/0x3a0
>                                 sp=e000000f3dfcfe20 bsp=e000000f3dfc1250
>  [<a00000010025e5e0>] sys_write+0x80/0x100
>                                 sp=e000000f3dfcfe20 bsp=e000000f3dfc11d0
>  [<a00000010000bf20>] ia64_ret_from_syscall+0x0/0x20
>                                 sp=e000000f3dfcfe30 bsp=e000000f3dfc11d0
>  [<a000000000040720>] __kernel_syscall_via_break+0x0/0x20
>                                 sp=e000000f3dfd0000 bsp=e000000f3dfc11d0
> Disabling lock debugging due to kernel taint
> 
> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
> Signed-off-by: Jiang Liu <liuj97@gmail.com>
> ---
>  drivers/pci/pcie/aer/aer_inject.c |   21 +++++++++++++++++++++
>  1 files changed, 21 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aer/aer_inject.c b/drivers/pci/pcie/aer/aer_inject.c
> index 5222986..fc28785 100644
> --- a/drivers/pci/pcie/aer/aer_inject.c
> +++ b/drivers/pci/pcie/aer/aer_inject.c
> @@ -109,6 +109,19 @@ static struct aer_error *__find_aer_error_by_dev(struct pci_dev *dev)
>  	return __find_aer_error((u16)domain, dev->bus->number, dev->devfn);
>  }
> 
> +static bool pci_is_upstream_bus(struct pci_bus *bus, struct pci_bus *up_bus)
> +{
> +	struct pci_bus *pbus = bus->parent;
> +
> +	while (pbus) {
> +		if (pbus == up_bus)
> +			return true;
> +		pbus = pbus->parent;
> +	}
> +
> +	return false;
> +}
> +
>  /* inject_lock must be held before calling */
>  static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
>  {
> @@ -118,6 +131,13 @@ static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
>  		if (bus_ops->bus == bus)
>  			return bus_ops->ops;
>  	}
> +
> +	/* here can't find bus_ops, fall back to get bus_ops of upstream bus */
> +	list_for_each_entry(bus_ops, &pci_bus_ops_list, list) {
> +		if (pci_is_upstream_bus(bus, bus_ops->bus))
> +			return bus_ops->ops;
> +	}
> +
>  	return NULL;
>  }
> 
> @@ -506,6 +526,7 @@ static struct miscdevice aer_inject_device = {
>  	.fops = &aer_inject_fops,
>  };
> 
> +
>  static int __init aer_inject_init(void)
>  {
>  	return misc_register(&aer_inject_device);

After

# rmmod aer_inject

What will happen?

Best Regards,
Huang Ying