netdev - Re: [PATCH net-next] bonding: make slave status notifications GFP

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Date:	Thu, 6 Mar 2014 10:02:06 +0800
From:	Ding Tianhong <dingtianhong@...wei.com>
To:	Veaceslav Falico <vfalico@...hat.com>, <netdev@...r.kernel.org>
CC:	Thomas Glanzmann <thomas@...nzmann.de>,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [PATCH net-next] bonding: make slave status notifications GFP_ATOMIC

On 2014/3/5 21:15, Veaceslav Falico wrote:
> Currently we're using GFP_KERNEL, however there are some path(s) where we
> can hold some spinlocks, specifically bond->curr_slave_lock:
> 
> [    4.722916] BUG: sleeping function called from invalid context at mm/slub.c:965
> [    4.724438] in_atomic(): 1, irqs_disabled(): 0, pid: 940, name: ifup-eth
> [    4.726034] 5 locks held by ifup-eth/940:
> ...snip...
> [    4.734646]  #4:  (&bond->curr_slave_lock){+...+.}, at: [<ffffffffa00badc6>] bond_enslave+0xda6/0xdd0 [bonding]
> ...snip...
> [    4.759081]  [<ffffffffa00b6f11>] bond_change_active_slave+0x191/0x3b0 [bonding]
> [    4.760917]  [<ffffffffa00b7227>] bond_select_active_slave+0xf7/0x1d0 [bonding]
> [    4.762751]  [<ffffffffa00badce>] bond_enslave+0xdae/0xdd0 [bonding]
> ...snip...
> 
> As it's out of hot path and is a really rare event - change the gfp_t flags
> to GFP_ATOMIC to avoid sleeping under spinlock.
> 
> CC: Thomas Glanzmann <thomas@...nzmann.de>
> CC: Ding Tianhong <dingtianhong@...wei.com>
> CC: Jay Vosburgh <fubar@...ibm.com>
> CC: Andy Gospodarek <andy@...yhouse.net>
> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
> ---
>  drivers/net/bonding/bonding.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
> index 4303628..4cd451d 100644
> --- a/drivers/net/bonding/bonding.h
> +++ b/drivers/net/bonding/bonding.h
> @@ -292,7 +292,7 @@ static inline void bond_set_active_slave(struct slave *slave)
>  {
>  	if (slave->backup) {
>  		slave->backup = 0;
> -		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_KERNEL);
> +		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_ATOMIC);
>  	}
>  }
>  
> @@ -300,7 +300,7 @@ static inline void bond_set_backup_slave(struct slave *slave)
>  {
>  	if (!slave->backup) {
>  		slave->backup = 1;
> -		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_KERNEL);
> +		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_ATOMIC);
>  	}
>  }
>  

Acked-by: Ding Tianhong <dingtianhong@...wei.com>

> 


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