Bug 29802

On an embedded system, (beagleboard using Asix CONFIG_USB_NET_AX8817X statically compiled,  usb/ethernet bridge, rootfs over nfs),  : 

[    6.817382] usb 1-2.4: new high speed USB device using ehci-omap and address 3
[    6.940979] usb 1-2.4: rpm_resume flags 0x0
[    6.945373] usb 1-2.4: rpm_resume returns 1
[    6.961700] usb 1-2.4: New USB device found, idVendor=0b95, idProduct=772a
[    6.968963] usb 1-2.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[    6.976684] usb 1-2.4: Product: AX88772 
[    6.980834] usb 1-2.4: Manufacturer: ASIX Elec. Corp.
[    6.986145] usb 1-2.4: SerialNumber: 000065
[    6.996917] usb 1-2.4: rpm_resume flags 0x4
[    7.001312] usb 1-2.4: rpm_resume returns 1
[    7.007507] usb 1-2.4: rpm_resume flags 0x4
[    7.011901] usb 1-2.4: rpm_resume returns 1
[    7.040679] mmc0: new SD card at address 9ffc
[    7.049255] mmcblk0: mmc0:9ffc SD01G 968 MiB 
[    7.061950]  mmcblk0: p1 p2
[    7.259307] usb usb2: rpm_suspend flags 0x9
[    7.263732] usb usb2: rpm_suspend returns 0
[    7.268310] usb usb2: rpm_suspend flags 0xa
[    7.272735] usb usb2: rpm_suspend returns 0
[    7.945953] asix 1-2.4:1.0: eth0: register 'asix' at usb-ehci-omap.0-2.4, ASIX AX88772 USB 
2.0 Ethernet, 00:00:00:00:00:65                                                              
[    7.957794] asix 1-2.4:1.0: rpm_suspend flags 0x4
[    7.962738] asix 1-2.4:1.0: rpm_suspend returns 0
[    7.967956] hub 1-2:1.0: rpm_resume flags 0x4
[    7.972534] hub 1-2:1.0: rpm_resume returns 1
[    7.977386] hub 1-2:1.0: rpm_suspend flags 0x4
[    7.982055] hub 1-2:1.0: rpm_suspend returns 0
[    8.333007] asix 1-2.4:1.0: rpm_resume flags 0x4
[    8.337890] asix 1-2.4:1.0: rpm_resume returns 0
[    8.343933] eth0: link down
[    9.368652] Sending DHCP requests .
[    9.949462] asix 1-2.4:1.0: rpm_resume flags 0x4
[    9.954498] asix 1-2.4:1.0: rpm_resume returns 1
[    9.961425] eth0: link up, 100Mbps, full-duplex, lpa 0x45E1
[   12.134307] .
[   12.135864] asix 1-2.4:1.0: rpm_resume flags 0x5
[   12.140869] asix 1-2.4:1.0: rpm_resume returns 1
[   12.649963] ,
[   12.651489] asix 1-2.4:1.0: rpm_resume flags 0x5
[   12.656524] asix 1-2.4:1.0: rpm_resume returns 1
[   12.665618]  OK
[   12.667480] IP-Config: Got DHCP answer from 0.0.0.0, my address is 192.168.1.102
[   12.678771] IP-Config: Complete:
[   12.682250]      device=eth0, addr=192.168.1.102, mask=255.255.255.0, gw=192.168.1.1,
[   12.690246]      host=192.168.1.102, domain=, nis-domain=(none),
[   12.696533]      bootserver=0.0.0.0, rootserver=192.168.1.106, rootpath=, mtu=576
[   12.715637] asix 1-2.4:1.0: rpm_resume flags 0x5
[   12.720489] asix 1-2.4:1.0: rpm_resume returns 1
[   12.725830] asix 1-2.4:1.0: rpm_resume flags 0x5
[   12.730651] asix 1-2.4:1.0: rpm_resume returns 1
[   12.742034] asix 1-2.4:1.0: rpm_resume flags 0x5
[   12.746887] asix 1-2.4:1.0: rpm_resume returns 1
[   12.752075] asix 1-2.4:1.0: rpm_resume flags 0x5
[   12.756927] asix 1-2.4:1.0: rpm_resume returns 1
:
:
(the last 2 lines keep repeating)

The system continues to work, the messages seem to be associated with activity on the network. But it slows down the system to the point of being unusable. 

This is a regression introduced in 2.6.37-rc1 and was bisected to : 

commit 63defa73c8c1193c1273474440c30d34c2524597
Author: Ming Lei <tom.leiming@gmail.com>
Date:   Mon Nov 15 15:56:54 2010 -0500

    USB: use the no_callbacks flag for interfaces
    
    Call pm_runtime_no_callbacks to set no_callbacks flag for USB
    interfaces.  Since interfaces cannot be power-managed separately from
    their parent devices, there's no reason for the runtime-PM core to
    invoke any callbacks for them.
    
    Signed-off-by: Ming Lei <tom.leiming@gmail.com>
    Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

BR
Abhishek