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Message-ID: <20131029073631.GA16894@redhat.com>
Date: Tue, 29 Oct 2013 09:36:31 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: rusty@...tcorp.com.au, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Wanlong Gao <gaowanlong@...fujitsu.com>
Subject: Re: [PATCH net] virtio-net: correctly handle cpu hotplug notifier
during resuming
On Tue, Oct 29, 2013 at 03:11:07PM +0800, Jason Wang wrote:
> commit 3ab098df35f8b98b6553edc2e40234af512ba877 (virtio-net: don't respond to
> cpu hotplug notifier if we're not ready) tries to bypass the cpu hotplug
> notifier by checking the config_enable and does nothing is it was false. So it
> need to try to hold the config_lock mutex which may happen in atomic
> environment which leads the following warnings:
>
> [ 622.944441] CPU0 attaching NULL sched-domain.
> [ 622.944446] CPU1 attaching NULL sched-domain.
> [ 622.944485] CPU0 attaching NULL sched-domain.
> [ 622.950795] BUG: sleeping function called from invalid context at kernel/mutex.c:616
> [ 622.950796] in_atomic(): 1, irqs_disabled(): 1, pid: 10, name: migration/1
> [ 622.950796] no locks held by migration/1/10.
> [ 622.950798] CPU: 1 PID: 10 Comm: migration/1 Not tainted 3.12.0-rc5-wl-01249-gb91e82d #317
> [ 622.950799] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> [ 622.950802] 0000000000000000 ffff88001d42dba0 ffffffff81a32f22 ffff88001bfb9c70
> [ 622.950803] ffff88001d42dbb0 ffffffff810edb02 ffff88001d42dc38 ffffffff81a396ed
> [ 622.950805] 0000000000000046 ffff88001d42dbe8 ffffffff810e861d 0000000000000000
> [ 622.950805] Call Trace:
> [ 622.950810] [<ffffffff81a32f22>] dump_stack+0x54/0x74
> [ 622.950815] [<ffffffff810edb02>] __might_sleep+0x112/0x114
> [ 622.950817] [<ffffffff81a396ed>] mutex_lock_nested+0x3c/0x3c6
> [ 622.950818] [<ffffffff810e861d>] ? up+0x39/0x3e
> [ 622.950821] [<ffffffff8153ea7c>] ? acpi_os_signal_semaphore+0x21/0x2d
> [ 622.950824] [<ffffffff81565ed1>] ? acpi_ut_release_mutex+0x5e/0x62
> [ 622.950828] [<ffffffff816d04ec>] virtnet_cpu_callback+0x33/0x87
> [ 622.950830] [<ffffffff81a42576>] notifier_call_chain+0x3c/0x5e
> [ 622.950832] [<ffffffff810e86a8>] __raw_notifier_call_chain+0xe/0x10
> [ 622.950835] [<ffffffff810c5556>] __cpu_notify+0x20/0x37
> [ 622.950836] [<ffffffff810c5580>] cpu_notify+0x13/0x15
> [ 622.950838] [<ffffffff81a237cd>] take_cpu_down+0x27/0x3a
> [ 622.950841] [<ffffffff81136289>] stop_machine_cpu_stop+0x93/0xf1
> [ 622.950842] [<ffffffff81136167>] cpu_stopper_thread+0xa0/0x12f
> [ 622.950844] [<ffffffff811361f6>] ? cpu_stopper_thread+0x12f/0x12f
> [ 622.950847] [<ffffffff81119710>] ? lock_release_holdtime.part.7+0xa3/0xa8
> [ 622.950848] [<ffffffff81135e4b>] ? cpu_stop_should_run+0x3f/0x47
> [ 622.950850] [<ffffffff810ea9b0>] smpboot_thread_fn+0x1c5/0x1e3
> [ 622.950852] [<ffffffff810ea7eb>] ? lg_global_unlock+0x67/0x67
> [ 622.950854] [<ffffffff810e36b7>] kthread+0xd8/0xe0
> [ 622.950857] [<ffffffff81a3bfad>] ? wait_for_common+0x12f/0x164
> [ 622.950859] [<ffffffff810e35df>] ? kthread_create_on_node+0x124/0x124
> [ 622.950861] [<ffffffff81a45ffc>] ret_from_fork+0x7c/0xb0
> [ 622.950862] [<ffffffff810e35df>] ? kthread_create_on_node+0x124/0x124
> [ 622.950876] smpboot: CPU 1 is now offline
> [ 623.194556] SMP alternatives: lockdep: fixing up alternatives
> [ 623.194559] smpboot: Booting Node 0 Processor 1 APIC 0x1
> ...
>
> A correct fix is to unregister the hotcpu notifier during restore and register a
> new one in resume.
>
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>
> Tested-by: Fengguang Wu <fengguang.wu@...el.com>
> Cc: Wanlong Gao <gaowanlong@...fujitsu.com>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
Acked-by: Michael S. Tsirkin <mst@...hat.com>
BTW there's a new Fixes: tag, you might want to use it
in the future.
> ---
> This patch is needed for 3.8 and above.
> ---
> drivers/net/virtio_net.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 9fbdfcd..bbc9cb8 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1118,11 +1118,6 @@ static int virtnet_cpu_callback(struct notifier_block *nfb,
> {
> struct virtnet_info *vi = container_of(nfb, struct virtnet_info, nb);
>
> - mutex_lock(&vi->config_lock);
> -
> - if (!vi->config_enable)
> - goto done;
> -
> switch(action & ~CPU_TASKS_FROZEN) {
> case CPU_ONLINE:
> case CPU_DOWN_FAILED:
> @@ -1136,8 +1131,6 @@ static int virtnet_cpu_callback(struct notifier_block *nfb,
> break;
> }
>
> -done:
> - mutex_unlock(&vi->config_lock);
> return NOTIFY_OK;
> }
>
> @@ -1699,6 +1692,8 @@ static int virtnet_freeze(struct virtio_device *vdev)
> struct virtnet_info *vi = vdev->priv;
> int i;
>
> + unregister_hotcpu_notifier(&vi->nb);
> +
> /* Prevent config work handler from accessing the device */
> mutex_lock(&vi->config_lock);
> vi->config_enable = false;
> @@ -1747,6 +1742,10 @@ static int virtnet_restore(struct virtio_device *vdev)
> virtnet_set_queues(vi, vi->curr_queue_pairs);
> rtnl_unlock();
>
> + err = register_hotcpu_notifier(&vi->nb);
> + if (err)
> + return err;
> +
> return 0;
> }
> #endif
> --
> 1.8.1.2
--
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