netdev - Re: [PATCH 2/2] ucc_geth: Fix deadlock

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Date:	Fri, 12 Nov 2010 17:09:47 +0300
From:	Anton Vorontsov <cbouatmailru@...il.com>
To:	Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>
Cc:	linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] ucc_geth: Fix deadlock

On Fri, Nov 12, 2010 at 02:55:09PM +0100, Joakim Tjernlund wrote:
> This script:
>  while [ 1==1 ] ; do ifconfig eth0 up; usleep 1950000 ;ifconfig eth0 down; dmesg -c ;done
> causes in just a second or two:
> INFO: task ifconfig:572 blocked for more than 120 seconds.
[...]
> The reason appears to be ucc_geth_stop meets adjust_link as the
> PHY reports PHY changes. I belive adjust_link hangs somewhere,
> holding the PHY lock, because ucc_geth_stop disabled the
> controller HW.
> Fix is to stop the PHY before disabling the controller.
> 
> Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>

It's unclear where exactly adjust_link() hangs, but the patch
looks as the right thing overall.

Thanks!

Reviewed-by: Anton Vorontsov <cbouatmailru@...il.com>

> ---
>  drivers/net/ucc_geth.c |   10 +++++++---
>  1 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
> index 6c254ed..06a5db3 100644
> --- a/drivers/net/ucc_geth.c
> +++ b/drivers/net/ucc_geth.c
> @@ -2050,12 +2050,16 @@ static void ucc_geth_stop(struct ucc_geth_private *ugeth)
>  
>  	ugeth_vdbg("%s: IN", __func__);
>  
> +	/*
> +	 * Tell the kernel the link is down.
> +	 * Must be done before disabling the controller
> +	 * or deadlock may happen.
> +	 */
> +	phy_stop(phydev);
> +
>  	/* Disable the controller */
>  	ugeth_disable(ugeth, COMM_DIR_RX_AND_TX);
>  
> -	/* Tell the kernel the link is down */
> -	phy_stop(phydev);
> -
>  	/* Mask all interrupts */
>  	out_be32(ugeth->uccf->p_uccm, 0x00000000);
--
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