net/ns: put workqueue of cleanup_net sleep for a while when notify.

hulk inclusion
category: bugfix
bugzilla: 186807 https://gitee.com/openeuler/kernel/issues/I5ATLD
CVE: NA

--------------------------------

When we clean up namespace, we have to notify every netdevice that
dev is down. If device that registered too many, the notify time will
take too many CPU time, It will course CPU soft-lockup issue. The
reprocedure is followed:
NIFS=50
for ((i=0; i<$NIFS; i++))
do
        ip netns add dummy-ns$i
        ip netns exec dummy-ns$i ip link set lo up
done

for ((j=0; j<$NIFS; j++))
do
        for ((i=0; i<1000; i++))
        do
                if=eth$j$i
                ip netns exec dummy-ns$j ip link add $if type dummy
                ip netns exec dummy-ns$j ip link set $if up
                done
done

for ((i=0; i<$NIFS; i++))
do
        ip netns del dummy-ns$i
done
The test will result in the following stack. So clean up work must
sleep for a while when notify device down/change.

watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [kworker/u8:5:288]
Modules linked in:
CPU: 0 PID: 288 Comm: kworker/u8:5 Tainted: G    B             5.10.0+ #5
Hardware name: linux,dummy-virt (DT)
Workqueue: netns cleanup_net
pstate: 20000005 (nzCv daif -PAN -UAO -TCO BTYPE=--)
pc : atomic_set include/asm-generic/atomic-instrumented.h:46 [inline]
pc : __alloc_skb+0x268/0x450 net/core/skbuff.c:241
lr : atomic_set include/asm-generic/atomic-instrumented.h:46 [inline]
lr : __alloc_skb+0x268/0x450 net/core/skbuff.c:241
sp : ffff000015607610
x29: ffff000015607610 x28: 00000000ffffffff
x27: 0000000000000001 x26: ffff0000cc9400e0
x25: ffff0000c745c1be x24: 1fffe00002ac0ed0
x23: 0000000000000000 x22: ffff0000cc9400c0
x21: ffff0000c745c234 x20: ffff0000cc940000
x19: ffff0000c745c140 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000
x15: 0000000000000000 x14: 1fffe00002ac0f00
x13: 0000000000000000 x12: ffff80001992801d
x11: 1fffe0001992801c x10: ffff80001992801c
x9 : dfffa00000000000 x8 : ffff0000cc9400e3
x7 : 0000000000000001 x6 : ffff80001992801c
x5 : ffff0000cc9400e0 x4 : dfffa00000000000
x3 : ffffa00011529a78 x2 : 0000000000000003
x1 : 0000000000000000 x0 : ffff0000cc9400e0
Call trace:
 atomic_set include/asm-generic/atomic-instrumented.h:46 [inline]
 __alloc_skb+0x268/0x450 net/core/skbuff.c:241
 alloc_skb include/linux/skbuff.h:1107 [inline]
 nlmsg_new include/net/netlink.h:958 [inline]
 rtmsg_ifa+0xf4/0x1e0 net/ipv4/devinet.c:1900
 __inet_del_ifa+0x328/0x650 net/ipv4/devinet.c:427
 inet_del_ifa net/ipv4/devinet.c:465 [inline]
 inetdev_destroy net/ipv4/devinet.c:318 [inline]
 inetdev_event+0x2ac/0xac0 net/ipv4/devinet.c:1599
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x94/0xd0 kernel/notifier.c:410
 call_netdevice_notifiers_info+0x9c/0x14c net/core/dev.c:2047
 call_netdevice_notifiers_extack net/core/dev.c:2059 [inline]
 call_netdevice_notifiers net/core/dev.c:2073 [inline]
 rollback_registered_many+0x3d0/0x7dc net/core/dev.c:9558
 unregister_netdevice_many+0x40/0x1b0 net/core/dev.c:10779
 default_device_exit_batch+0x24c/0x2a0 net/core/dev.c:11262
 ops_exit_list+0xb4/0xd0 net/core/net_namespace.c:192
 cleanup_net+0x2b8/0x540 net/core/net_namespace.c:608
 process_one_work+0x3ec/0xa40 kernel/workqueue.c:2279
 worker_thread+0x110/0x8b0 kernel/workqueue.c:2425
 kthread+0x1ac/0x1fc kernel/kthread.c:313
 ret_from_fork+0x10/0x18 arch/arm64/kernel/entry.S:1034
Signed-off-by: NZhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/core/dev.c

@@ -1648,6 +1648,7 @@ void dev_close_many(struct list_head *head, bool unlink)
 		call_netdevice_notifiers(NETDEV_DOWN, dev);
 		if (unlink)
 			list_del_init(&dev->close_list);
+		cond_resched();
 	}
 }
 EXPORT_SYMBOL(dev_close_many);
@@ -9591,6 +9592,7 @@ static void rollback_registered_many(struct list_head *head)
 		/* Remove XPS queueing entries */
 		netif_reset_xps_queues_gt(dev, 0);
 #endif
+		cond_resched();
 	}
 
 	synchronize_net();