netdev - Re: [PATCH net v2 1/1] ice: avoid bonding causing auxiliary plug/unplug under RTNL lock

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Message-ID: <b944d1d4-7f90-dcef-231c-91bb031a4275@intel.com>
Date:   Thu, 16 Feb 2023 17:35:03 -0800
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <edumazet@...gle.com>
CC:     Dave Ertman <david.m.ertman@...el.com>, <netdev@...r.kernel.org>,
        <shiraz.saleem@...el.com>, <mustafa.ismail@...el.com>,
        <jgg@...dia.com>, <leonro@...dia.com>,
        <linux-rdma@...r.kernel.org>, <poros@...hat.com>,
        <ivecera@...hat.com>, <stable@...r.kernel.org>,
        Jaroslav Pulchart <jaroslav.pulchart@...ddata.com>
Subject: Re: [PATCH net v2 1/1] ice: avoid bonding causing auxiliary
 plug/unplug under RTNL lock

On 2/16/2023 4:42 PM, Tony Nguyen wrote:
> From: Dave Ertman <david.m.ertman@...el.com>
> 
> RDMA is not supported in ice on a PF that has been added to a bonded
> interface. To enforce this, when an interface enters a bond, we unplug
> the auxiliary device that supports RDMA functionality.  This unplug
> currently happens in the context of handling the netdev bonding event.
> This event is sent to the ice driver under RTNL context.  This is causing
> a deadlock where the RDMA driver is waiting for the RTNL lock to complete
> the removal.
> 
> Defer the unplugging/re-plugging of the auxiliary device to the service
> task so that it is not performed under the RTNL lock context.
> 
> Cc: stable@...r.kernel.org # 6.1.x
> Reported-by: Jaroslav Pulchart <jaroslav.pulchart@...ddata.com>
> Link: https://lore.kernel.org/netdev/CAK8fFZ6A_Gphw_3-QMGKEFQk=sfCw1Qmq0TVZK3rtAi7vb621A@mail.gmail.com/
> Fixes: 5cb1ebdbc434 ("ice: Fix race condition during interface enslave")
> Fixes: 4eace75e0853 ("RDMA/irdma: Report the correct link speed")
> Signed-off-by: Dave Ertman <david.m.ertman@...el.com>
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> ---
> v2:
>   (Removed from original pull request)
> - Reversed order of bit processing in ice_service_task for PLUG/UNPLUG

Please ignore/drop this. Just saw that this change doesn't solve the issue.

https://lore.kernel.org/intel-wired-lan/ygay1oxikvo.fsf@localhost/T/#m83d7162b2830f248a51d121965443687d7f54654

Thanks,
Tony

> v1: https://lore.kernel.org/netdev/20230131213703.1347761-2-anthony.l.nguyen@intel.com/
> 
>   drivers/net/ethernet/intel/ice/ice.h      | 14 +++++---------
>   drivers/net/ethernet/intel/ice/ice_main.c | 19 ++++++++-----------
>   2 files changed, 13 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
> index 713069f809ec..3cad5e6b2ad1 100644
> --- a/drivers/net/ethernet/intel/ice/ice.h
> +++ b/drivers/net/ethernet/intel/ice/ice.h
> @@ -506,6 +506,7 @@ enum ice_pf_flags {
>   	ICE_FLAG_VF_VLAN_PRUNING,
>   	ICE_FLAG_LINK_LENIENT_MODE_ENA,
>   	ICE_FLAG_PLUG_AUX_DEV,
> +	ICE_FLAG_UNPLUG_AUX_DEV,
>   	ICE_FLAG_MTU_CHANGED,
>   	ICE_FLAG_GNSS,			/* GNSS successfully initialized */
>   	ICE_PF_FLAGS_NBITS		/* must be last */
> @@ -950,16 +951,11 @@ static inline void ice_set_rdma_cap(struct ice_pf *pf)
>    */
>   static inline void ice_clear_rdma_cap(struct ice_pf *pf)
>   {
> -	/* We can directly unplug aux device here only if the flag bit
> -	 * ICE_FLAG_PLUG_AUX_DEV is not set because ice_unplug_aux_dev()
> -	 * could race with ice_plug_aux_dev() called from
> -	 * ice_service_task(). In this case we only clear that bit now and
> -	 * aux device will be unplugged later once ice_plug_aux_device()
> -	 * called from ice_service_task() finishes (see ice_service_task()).
> +	/* defer unplug to service task to avoid RTNL lock and
> +	 * clear PLUG bit so that pending plugs don't interfere
>   	 */
> -	if (!test_and_clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags))
> -		ice_unplug_aux_dev(pf);
> -
> +	clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags);
> +	set_bit(ICE_FLAG_UNPLUG_AUX_DEV, pf->flags);
>   	clear_bit(ICE_FLAG_RDMA_ENA, pf->flags);
>   }
>   #endif /* _ICE_H_ */
> diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
> index 8ec24f6cf6be..10d1c5b10d2a 100644
> --- a/drivers/net/ethernet/intel/ice/ice_main.c
> +++ b/drivers/net/ethernet/intel/ice/ice_main.c
> @@ -2316,18 +2316,15 @@ static void ice_service_task(struct work_struct *work)
>   		}
>   	}
>   
> -	if (test_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags)) {
> -		/* Plug aux device per request */
> -		ice_plug_aux_dev(pf);
> +	/* unplug aux dev per request, if an unplug request came in
> +	 * while processing a plug request, this will handle it
> +	 */
> +	if (test_and_clear_bit(ICE_FLAG_UNPLUG_AUX_DEV, pf->flags))
> +		ice_unplug_aux_dev(pf);
>   
> -		/* Mark plugging as done but check whether unplug was
> -		 * requested during ice_plug_aux_dev() call
> -		 * (e.g. from ice_clear_rdma_cap()) and if so then
> -		 * plug aux device.
> -		 */
> -		if (!test_and_clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags))
> -			ice_unplug_aux_dev(pf);
> -	}
> +	/* Plug aux device per request */
> +	if (test_and_clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags))
> +		ice_plug_aux_dev(pf);
>   
>   	if (test_and_clear_bit(ICE_FLAG_MTU_CHANGED, pf->flags)) {
>   		struct iidc_event *event;