netdev - Re: [PATCH 2.6.28] RDMA/cxgb3: deadlock in iw_cxgb3 can cause hang when configuring interface.

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Message-ID: <49137D59.9070306@chelsio.com>
Date:	Thu, 06 Nov 2008 15:27:21 -0800
From:	Divy Le Ray <divy@...lsio.com>
To:	Steve Wise <swise@...ngridcomputing.com>
CC:	rdreier@...co.com, jeff@...zik.org, wenxiong@...ibm.com,
	general@...ts.openfabrics.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2.6.28] RDMA/cxgb3: deadlock in iw_cxgb3 can cause hang
 when configuring interface.

Steve Wise wrote:
> From: Steve Wise <swise@...ngridcomputing.com>
>
> When the iw_cxgb3 module's cxgb3_client "add" func gets called by the
> cxgb3 module, the iwarp driver ends up calling the ethtool ops get_drvinfo
> function in cxgb3 to get the fw version and other info.  Currently the
> iwarp driver grabs the rtnl lock around this down call to serialize.
> As of 2.6.27 or so, things changed such that the rtnl lock is held around
> the call to the netdev driver open function.  Also the cxgb3_client "add"
> function doesn't get called if the device is down.  
>
> So, if you load cxgb3, then load iw_cxgb3, then ifconfig up the device,
> the iw_cxgb3 add func gets called with the rtnl_lock held.   If you
> load cxgb3, ifconfig up the device, then load iw_cxgb3, the add func
> gets called without the rtnl_lock held.  The former causes the deadlock,
> the latter does not.
>
> In addition, there are iw_cxgb3 sysfs handlers that also can call
> down into cxgb3 to gather the fw and hw versions.  These can be called
> concurrently on different processors and at any time.  Thus we need to
> push this serialization down in the cxgb3 driver get_drvinfo func.
>
> The fix is to remove rtnl lock usage, and use a per-device lock in cxgb3.
>
> Signed-off-by: Steve Wise <swise@...ngridcomputing.com>
>   

Acked-by: Divy Le Ray <divy@...lsio.com>

> ---
>
>  drivers/infiniband/hw/cxgb3/iwch_provider.c |    6 ------
>  drivers/net/cxgb3/cxgb3_main.c              |    2 ++
>  2 files changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/infiniband/hw/cxgb3/iwch_provider.c b/drivers/infiniband/hw/cxgb3/iwch_provider.c
> index ecff980..160ef48 100644
> --- a/drivers/infiniband/hw/cxgb3/iwch_provider.c
> +++ b/drivers/infiniband/hw/cxgb3/iwch_provider.c
> @@ -1102,9 +1102,7 @@ static u64 fw_vers_string_to_u64(struct iwch_dev *iwch_dev)
>  	char *cp, *next;
>  	unsigned fw_maj, fw_min, fw_mic;
>  
> -	rtnl_lock();
>  	lldev->ethtool_ops->get_drvinfo(lldev, &info);
> -	rtnl_unlock();
>  
>  	next = info.fw_version + 1;
>  	cp = strsep(&next, ".");
> @@ -1192,9 +1190,7 @@ static ssize_t show_fw_ver(struct device *dev, struct device_attribute *attr, ch
>  	struct net_device *lldev = iwch_dev->rdev.t3cdev_p->lldev;
>  
>  	PDBG("%s dev 0x%p\n", __func__, dev);
> -	rtnl_lock();
>  	lldev->ethtool_ops->get_drvinfo(lldev, &info);
> -	rtnl_unlock();
>  	return sprintf(buf, "%s\n", info.fw_version);
>  }
>  
> @@ -1207,9 +1203,7 @@ static ssize_t show_hca(struct device *dev, struct device_attribute *attr,
>  	struct net_device *lldev = iwch_dev->rdev.t3cdev_p->lldev;
>  
>  	PDBG("%s dev 0x%p\n", __func__, dev);
> -	rtnl_lock();
>  	lldev->ethtool_ops->get_drvinfo(lldev, &info);
> -	rtnl_unlock();
>  	return sprintf(buf, "%s\n", info.driver);
>  }
>  
> diff --git a/drivers/net/cxgb3/cxgb3_main.c b/drivers/net/cxgb3/cxgb3_main.c
> index 1ace41a..5e663cc 100644
> --- a/drivers/net/cxgb3/cxgb3_main.c
> +++ b/drivers/net/cxgb3/cxgb3_main.c
> @@ -1307,8 +1307,10 @@ static void get_drvinfo(struct net_device *dev, struct ethtool_drvinfo *info)
>  	u32 fw_vers = 0;
>  	u32 tp_vers = 0;
>  
> +	spin_lock(&adapter->stats_lock);
>  	t3_get_fw_version(adapter, &fw_vers);
>  	t3_get_tp_version(adapter, &tp_vers);
> +	spin_unlock(&adapter->stats_lock);
>  
>  	strcpy(info->driver, DRV_NAME);
>  	strcpy(info->version, DRV_VERSION);
>   

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