BUG_ON triggered by igb driver in latest kernel

[Yang Yingliang]

Hi,

I use netmap with igb card in kernel 3.13-rc7, it triggered a bug_on.

The reason is that the patch "diff--igb--30b00--99999" remove the
napi_disable() in igb_down(). When netmap calls igb_up()->napi_enable(),
a bug_on is triggered.

-----------------------------------------------------------------------

Here is the calltrace:

PANIC: "kernel BUG at include/linux/netdevice.h:502!"

PID: 3200   TASK: ffff880069490410  CPU: 0   COMMAND: "pkt-gen"
 #0 [ffff880069493a00] machine_kexec at ffffffff81033c1d
 #1 [ffff880069493a50] crash_kexec at ffffffff810ad5a3
 #2 [ffff880069493b20] oops_end at ffffffff81434650
 #3 [ffff880069493b50] die at ffffffff81005716
 #4 [ffff880069493b80] do_trap at ffffffff814341dc
 #5 [ffff880069493bd0] do_invalid_op at ffffffff81003540
 #6 [ffff880069493c70] invalid_op at ffffffff8143ace8
    [exception RIP: igb_up+344]
    RIP: ffffffffa030ed88  RSP: ffff880069493d28  RFLAGS: 00010246
    RAX: 0000000000000000  RBX: ffff88007ac22840  RCX: 0000000000000000
    RDX: ffff880037fbdc60  RSI: ffff88007ac22840  RDI: 0000000000000002
    RBP: ffff880069493d38   R8: 0000000000000000   R9: 0000000000000006
    R10: 000000000000000a  R11: 0000000000000006  R12: ffff88007ac22000
    R13: ffff8800377e7800  R14: ffff88007ac22840  R15: 0000000000000001
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
 #7 [ffff880069493d20] igb_up at ffffffffa030ec41 [igb]
 #8 [ffff880069493d40] igb_netmap_reg at ffffffffa030fa0d [igb]
 #9 [ffff880069493d80] netmap_do_regif at ffffffffa02d3915 [netmap_lin]
#10 [ffff880069493dc0] linux_netmap_ioctl at ffffffffa02d4628 [netmap_lin]
#11 [ffff880069493eb0] do_vfs_ioctl at ffffffff81143d84
#12 [ffff880069493f30] sys_ioctl at ffffffff811442a1
#13 [ffff880069493f80] system_call_fastpath at ffffffff81439c62