Subject: Re: [PATCH] sky2: initialize napi before registering device

From: Stephen Hemminger <[email-masked]>
Date: Sat, 25 Jan 2014 17:01:20 -0800

On Sat, 25 Jan 2014 11:34:54 +0100
Stanislaw Gruszka <[email-masked]> wrote:

> There is race condition when call netif_napi_add() after
> register_netdevice(), as ->open() can be called without napi initialized
> and trigger BUG_ON() on napi_enable(), like on below messages:
> 
> [    9.699863] sky2: driver version 1.30
> [    9.699960] sky2 0000:02:00.0: Yukon-2 EC Ultra chip revision 2
> [    9.700020] sky2 0000:02:00.0: irq 45 for MSI/MSI-X
> [    9.700498] ------------[ cut here ]------------
> [    9.703391] kernel BUG at include/linux/netdevice.h:501!
> [    9.703391] invalid opcode: 0000 [#1] PREEMPT SMP
> <snip>
> [    9.830018] Call Trace:
> [    9.830018]  [<fa996169>] sky2_open+0x309/0x360 [sky2]
> [    9.830018]  [<c1007210>] ? via_no_dac+0x40/0x40
> [    9.830018]  [<c1007210>] ? via_no_dac+0x40/0x40
> [    9.830018]  [<c135ed4b>] __dev_open+0x9b/0x120
> [    9.830018]  [<c1431cbe>] ? _raw_spin_unlock_bh+0x1e/0x20
> [    9.830018]  [<c135efd9>] __dev_change_flags+0x89/0x150
> [    9.830018]  [<c135f148>] dev_change_flags+0x18/0x50
> [    9.830018]  [<c13bb8e0>] devinet_ioctl+0x5d0/0x6e0
> [    9.830018]  [<c13bcced>] inet_ioctl+0x6d/0xa0
> 
> To fix the problem patch changes the order of initialization.
> 
> Bug report:
> https://bugzilla.kernel.org/show_bug.cgi?id=67151
> 
> Reported-and-tested-by: [email-masked]
> Signed-off-by: Stanislaw Gruszka <[email-masked]>

That looks good, problem was introduced years ago.
I wonder if netif_napi_del() should be in unwind if registration
of either devices fails?