linux-kernel - Re: [PATCH 2.6.27-rc8 3/6] e1000e: remove phy read from inside spinlock

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Date:	Fri, 3 Oct 2008 02:37:25 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jesse Brandeburg <jesse.brandeburg@...el.com>
cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, arjan@...ux.intel.com, airlied@...il.com,
	davem@...emloft.net, jeff@...zik.org
Subject: Re: [PATCH 2.6.27-rc8 3/6] e1000e: remove phy read from inside
 spinlock

On Thu, 2 Oct 2008, Jesse Brandeburg wrote:

> thanks to tglx, we're finding some interesting reentrancy issues.
> this patch removes the phy read from inside a spinlock, paving
> the way for removing the spinlock completely.  The phy read was
> only feeding a statistic that wasn't used.
> 
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
> CC: Thomas Gleixner <tglx@...utronix.de>

Acked-by: Thomas Gleixner <tglx@...utronix.de>

> ---
> 
>  drivers/net/e1000e/ethtool.c |    6 +++++-
>  drivers/net/e1000e/netdev.c  |   13 -------------
>  2 files changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/e1000e/ethtool.c b/drivers/net/e1000e/ethtool.c
> index 5ed8e13..33a3ff1 100644
> --- a/drivers/net/e1000e/ethtool.c
> +++ b/drivers/net/e1000e/ethtool.c
> @@ -432,6 +432,10 @@ static void e1000_get_regs(struct net_device *netdev,
>  	regs_buff[11] = er32(TIDV);
>  
>  	regs_buff[12] = adapter->hw.phy.type;  /* PHY type (IGP=1, M88=0) */
> +
> +	/* ethtool doesn't use anything past this point, so all this
> +	 * code is likely legacy junk for apps that may or may not
> +	 * exist */
>  	if (hw->phy.type == e1000_phy_m88) {
>  		e1e_rphy(hw, M88E1000_PHY_SPEC_STATUS, &phy_data);
>  		regs_buff[13] = (u32)phy_data; /* cable length */
> @@ -447,7 +451,7 @@ static void e1000_get_regs(struct net_device *netdev,
>  		regs_buff[22] = adapter->phy_stats.receive_errors;
>  		regs_buff[23] = regs_buff[13]; /* mdix mode */
>  	}
> -	regs_buff[21] = adapter->phy_stats.idle_errors;  /* phy idle errors */
> +	regs_buff[21] = 0; /* was idle_errors */
>  	e1e_rphy(hw, PHY_1000T_STATUS, &phy_data);
>  	regs_buff[24] = (u32)phy_data;  /* phy local receiver status */
>  	regs_buff[25] = regs_buff[24];  /* phy remote receiver status */
> diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
> index 803545b..835b692 100644
> --- a/drivers/net/e1000e/netdev.c
> +++ b/drivers/net/e1000e/netdev.c
> @@ -2954,9 +2954,6 @@ void e1000e_update_stats(struct e1000_adapter *adapter)
>  	struct e1000_hw *hw = &adapter->hw;
>  	struct pci_dev *pdev = adapter->pdev;
>  	unsigned long irq_flags;
> -	u16 phy_tmp;
> -
> -#define PHY_IDLE_ERROR_COUNT_MASK 0x00FF
>  
>  	/*
>  	 * Prevent stats update while adapter is being reset, or if the pci
> @@ -3045,15 +3042,6 @@ void e1000e_update_stats(struct e1000_adapter *adapter)
>  
>  	/* Tx Dropped needs to be maintained elsewhere */
>  
> -	/* Phy Stats */
> -	if (hw->phy.media_type == e1000_media_type_copper) {
> -		if ((adapter->link_speed == SPEED_1000) &&
> -		   (!e1e_rphy(hw, PHY_1000T_STATUS, &phy_tmp))) {
> -			phy_tmp &= PHY_IDLE_ERROR_COUNT_MASK;
> -			adapter->phy_stats.idle_errors += phy_tmp;
> -		}
> -	}
> -
>  	/* Management Stats */
>  	adapter->stats.mgptc += er32(MGTPTC);
>  	adapter->stats.mgprc += er32(MGTPRC);
> @@ -3073,7 +3061,6 @@ static void e1000_phy_read_status(struct e1000_adapter *adapter)
>  	int ret_val;
>  	unsigned long irq_flags;
>  
> -
>  	spin_lock_irqsave(&adapter->stats_lock, irq_flags);
>  
>  	if ((er32(STATUS) & E1000_STATUS_LU) &&
> 
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