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Subject[PATCH net] virtio-net: correctly handle cpu hotplug notifier during resuming
Date
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@intel.com>
Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
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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