[Xen-devel] Re: [PATCH] xen: netfront: hold RTNL when updating features.

[David Miller <davem@xxxxxxxxxxxxx>]

From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Wed, 25 May 2011 08:56:02 +0100

> Konrad reports:
> [    0.930811] RTNL: assertion failed at 
> /home/konrad/ssd/linux/net/core/dev.c (5258)
> [    0.930821] Pid: 22, comm: xenwatch Not tainted 2.6.39-05193-gd762f43 #1
> [    0.930825] Call Trace:
> [    0.930834]  [<ffffffff8143bd0e>] __netdev_update_features+0xae/0xe0
> [    0.930840]  [<ffffffff8143dd41>] netdev_update_features+0x11/0x30
> [    0.930847]  [<ffffffffa0037105>] netback_changed+0x4e5/0x800 
> [xen_netfront]
> [    0.930854]  [<ffffffff8132a838>] xenbus_otherend_changed+0xa8/0xb0
> [    0.930860]  [<ffffffff8157ca99>] ? _raw_spin_unlock_irqrestore+0x19/0x20
> [    0.930866]  [<ffffffff8132adfe>] backend_changed+0xe/0x10
> [    0.930871]  [<ffffffff8132875a>] xenwatch_thread+0xba/0x180
> [    0.930876]  [<ffffffff810a8ba0>] ? wake_up_bit+0x40/0x40
> [    0.930881]  [<ffffffff813286a0>] ? split+0xf0/0xf0
> [    0.930886]  [<ffffffff810a8646>] kthread+0x96/0xa0
> [    0.930891]  [<ffffffff815855a4>] kernel_thread_helper+0x4/0x10
> [    0.930896]  [<ffffffff815846b3>] ? int_ret_from_sys_call+0x7/0x1b
> [    0.930901]  [<ffffffff8157cf61>] ? retint_restore_args+0x5/0x6
> [    0.930906]  [<ffffffff815855a0>] ? gs_change+0x13/0x13
> 
> This update happens in xenbus watch callback context and hence does not 
> already
> hold the rtnl. Take the lock as necessary.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

Applied.

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