Re: [patch net] devlink: change per-devlink netdev notifier to static one

[Jiri Pirko <jiri@resnulli.us>]

Mon, May 15, 2023 at 11:09:10AM CEST, m.szyprowski@samsung.com wrote:
>On 10.05.2023 16:46, Jiri Pirko wrote:
>> From: Jiri Pirko <jiri@nvidia.com>
>>
>> The commit 565b4824c39f ("devlink: change port event netdev notifier
>> from per-net to global") changed original per-net notifier to be
>> per-devlink instance. That fixed the issue of non-receiving events
>> of netdev uninit if that moved to a different namespace.
>> That worked fine in -net tree.
>>
>> However, later on when commit ee75f1fc44dd ("net/mlx5e: Create
>> separate devlink instance for ethernet auxiliary device") and
>> commit 72ed5d5624af ("net/mlx5: Suspend auxiliary devices only in
>> case of PCI device suspend") were merged, a deadlock was introduced
>> when removing a namespace with devlink instance with another nested
>> instance.
>>
>> Here there is the bad flow example resulting in deadlock with mlx5:
>> net_cleanup_work -> cleanup_net (takes down_read(&pernet_ops_rwsem) ->
>> devlink_pernet_pre_exit() -> devlink_reload() ->
>> mlx5_devlink_reload_down() -> mlx5_unload_one_devl_locked() ->
>> mlx5_detach_device() -> del_adev() -> mlx5e_remove() ->
>> mlx5e_destroy_devlink() -> devlink_free() ->
>> unregister_netdevice_notifier() (takes down_write(&pernet_ops_rwsem)
>>
>> Steps to reproduce:
>> $ modprobe mlx5_core
>> $ ip netns add ns1
>> $ devlink dev reload pci/0000:08:00.0 netns ns1
>> $ ip netns del ns1
>>
>> Resolve this by converting the notifier from per-devlink instance to
>> a static one registered during init phase and leaving it registered
>> forever. Use this notifier for all devlink port instances created
>> later on.
>>
>> Note what a tree needs this fix only in case all of the cited fixes
>> commits are present.
>>
>> Reported-by: Moshe Shemesh <moshe@nvidia.com>
>> Fixes: 565b4824c39f ("devlink: change port event netdev notifier from per-net to global")
>> Fixes: ee75f1fc44dd ("net/mlx5e: Create separate devlink instance for ethernet auxiliary device")
>> Fixes: 72ed5d5624af ("net/mlx5: Suspend auxiliary devices only in case of PCI device suspend")
>> Signed-off-by: Jiri Pirko <jiri@nvidia.com>
>
>This patch landed recently in linux-next as commit e93c9378e33f 
>("devlink: change per-devlink netdev notifier to static one"). 
>Unfortunately it causes serious regression with kernel compiled from 
>multi_v7_defconfig (ARM 32bit) on all my test boards. Here is a example 
>of the boot failure observed on QEMU's virt ARM 32bit machine:
>
>8<--- cut here ---
>Unable to handle kernel execution of memory at virtual address e5150010 
>when execute
>[e5150010] *pgd=4267a811, *pte=04750653, *ppte=04750453
>Internal error: Oops: 8000000f [#1] SMP ARM
>Modules linked in:
>CPU: 0 PID: 779 Comm: ip Not tainted 6.4.0-rc2-next-20230515 #6688
>Hardware name: Generic DT based system
>PC is at 0xe5150010
>LR is at notifier_call_chain+0x60/0x11c
>pc : [<e5150010>]    lr : [<c0365f50>]    psr: 60000013
>...
>Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
>Control: 10c5387d  Table: 4397806a  DAC: 00000051
>...
>Process ip (pid: 779, stack limit = 0x82b757b5)
>Stack: (0xe9201a00 to 0xe9202000)
>...
>  notifier_call_chain from raw_notifier_call_chain+0x18/0x20
>  raw_notifier_call_chain from __dev_open+0x74/0x190
>  __dev_open from __dev_change_flags+0x17c/0x1f4
>  __dev_change_flags from dev_change_flags+0x18/0x54
>  dev_change_flags from do_setlink+0x24c/0xefc
>  do_setlink from rtnl_newlink+0x534/0x818
>  rtnl_newlink from rtnetlink_rcv_msg+0x250/0x300
>  rtnetlink_rcv_msg from netlink_rcv_skb+0xb8/0x110
>  netlink_rcv_skb from netlink_unicast+0x1f8/0x2bc
>  netlink_unicast from netlink_sendmsg+0x1cc/0x44c
>  netlink_sendmsg from ____sys_sendmsg+0x9c/0x260
>  ____sys_sendmsg from ___sys_sendmsg+0x68/0x94
>  ___sys_sendmsg from sys_sendmsg+0x4c/0x88
>  sys_sendmsg from ret_fast_syscall+0x0/0x54
>Exception stack(0xe9201fa8 to 0xe9201ff0)

Thanks for the report. From the first sight, don't have a clue what may
be wrong. Debugging.


>...
>---[ end trace 0000000000000000 ]---
>[....] Configuring network interfaces...Segmentation fault
>ifup: failed to bring up lo
>
>
>Reverting $subject patch on top of linux next-20230515 fixes this issue.
>
>
>> ---
>>   net/devlink/core.c          | 16 +++++++---------
>>   net/devlink/devl_internal.h |  1 -
>>   net/devlink/leftover.c      |  5 ++---
>>   3 files changed, 9 insertions(+), 13 deletions(-)
>>
>> diff --git a/net/devlink/core.c b/net/devlink/core.c
>> index 777b091ef74d..0e58eee44bdb 100644
>> --- a/net/devlink/core.c
>> +++ b/net/devlink/core.c
>> @@ -204,11 +204,6 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
>>   	if (ret < 0)
>>   		goto err_xa_alloc;
>>   
>> -	devlink->netdevice_nb.notifier_call = devlink_port_netdevice_event;
>> -	ret = register_netdevice_notifier(&devlink->netdevice_nb);
>> -	if (ret)
>> -		goto err_register_netdevice_notifier;
>> -
>>   	devlink->dev = dev;
>>   	devlink->ops = ops;
>>   	xa_init_flags(&devlink->ports, XA_FLAGS_ALLOC);
>> @@ -233,8 +228,6 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
>>   
>>   	return devlink;
>>   
>> -err_register_netdevice_notifier:
>> -	xa_erase(&devlinks, devlink->index);
>>   err_xa_alloc:
>>   	kfree(devlink);
>>   	return NULL;
>> @@ -266,8 +259,6 @@ void devlink_free(struct devlink *devlink)
>>   	xa_destroy(&devlink->params);
>>   	xa_destroy(&devlink->ports);
>>   
>> -	WARN_ON_ONCE(unregister_netdevice_notifier(&devlink->netdevice_nb));
>> -
>>   	xa_erase(&devlinks, devlink->index);
>>   
>>   	devlink_put(devlink);
>> @@ -303,6 +294,10 @@ static struct pernet_operations devlink_pernet_ops __net_initdata = {
>>   	.pre_exit = devlink_pernet_pre_exit,
>>   };
>>   
>> +static struct notifier_block devlink_port_netdevice_nb __net_initdata = {
>> +	.notifier_call = devlink_port_netdevice_event,
>> +};
>> +
>>   static int __init devlink_init(void)
>>   {
>>   	int err;
>> @@ -311,6 +306,9 @@ static int __init devlink_init(void)
>>   	if (err)
>>   		goto out;
>>   	err = register_pernet_subsys(&devlink_pernet_ops);
>> +	if (err)
>> +		goto out;
>> +	err = register_netdevice_notifier(&devlink_port_netdevice_nb);
>>   
>>   out:
>>   	WARN_ON(err);
>> diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
>> index e133f423294a..62921b2eb0d3 100644
>> --- a/net/devlink/devl_internal.h
>> +++ b/net/devlink/devl_internal.h
>> @@ -50,7 +50,6 @@ struct devlink {
>>   	u8 reload_failed:1;
>>   	refcount_t refcount;
>>   	struct rcu_work rwork;
>> -	struct notifier_block netdevice_nb;
>>   	char priv[] __aligned(NETDEV_ALIGN);
>>   };
>>   
>> diff --git a/net/devlink/leftover.c b/net/devlink/leftover.c
>> index dffca2f9bfa7..cd0254968076 100644
>> --- a/net/devlink/leftover.c
>> +++ b/net/devlink/leftover.c
>> @@ -7073,10 +7073,9 @@ int devlink_port_netdevice_event(struct notifier_block *nb,
>>   	struct devlink_port *devlink_port = netdev->devlink_port;
>>   	struct devlink *devlink;
>>   
>> -	devlink = container_of(nb, struct devlink, netdevice_nb);
>> -
>> -	if (!devlink_port || devlink_port->devlink != devlink)
>> +	if (!devlink_port)
>>   		return NOTIFY_OK;
>> +	devlink = devlink_port->devlink;
>>   
>>   	switch (event) {
>>   	case NETDEV_POST_INIT:
>
>Best regards
>-- 
>Marek Szyprowski, PhD
>Samsung R&D Institute Poland
>