[3.8.y.z extended stable] Patch "virtio-net: correctly handle cpu hotplug notifier during resuming" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Fri Dec 6 23:08:00 UTC 2013


This is a note to let you know that I have just added a patch titled

    virtio-net: correctly handle cpu hotplug notifier during resuming

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.14.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6278adf113becfe506cd0955f600e27a1b67b06d Mon Sep 17 00:00:00 2001
From: Jason Wang <jasowang at redhat.com>
Date: Tue, 29 Oct 2013 15:11:07 +0800
Subject: virtio-net: correctly handle cpu hotplug notifier during resuming

[ Upstream commit ec9debbd9a88d8ea86c488d6ffcac419ee7d46d9 ]

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 at intel.com>
Tested-by: Fengguang Wu <fengguang.wu at intel.com>
Cc: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Cc: Rusty Russell <rusty at rustcorp.com.au>
Cc: Michael S. Tsirkin <mst at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>
Reviewed-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 848d26c..c3bcb4a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1076,11 +1076,6 @@ 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:
@@ -1094,8 +1089,6 @@ static int virtnet_cpu_callback(struct notifier_block *nfb,
 		break;
 	}

-done:
-	mutex_unlock(&vi->config_lock);
 	return NOTIFY_OK;
 }

@@ -1650,6 +1643,8 @@ 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;
@@ -1696,6 +1691,10 @@ static int virtnet_restore(struct virtio_device *vdev)

 	virtnet_set_queues(vi, vi->curr_queue_pairs);

+	err = register_hotcpu_notifier(&vi->nb);
+	if (err)
+		return err;
+
 	return 0;
 }
 #endif
--
1.8.3.2





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