[ofa-general] [PATCH 2.6.27] RDMA/cxgb3: Deadlock initializing the iw_cxgb3 device.

[Steve Wise]

From: Steve Wise <swise at opengridcomputing.com>

Running 'ifconfig up' on the cxgb3 interface with iw_cxgb3 loaded
causes a deadlock.  Apparently the rtnl lock is already held in
this path.  Function fw_supports_fastreg() was introduced in 2.6.27 to
conditionally set the IB_DEVICE_MEM_MGT_EXTENSIONS bit iff the firmware
was at 7.0 or greater.  This function acquires the rtnl lock and thus
can cause a deadlock.  Further, if iw_cxgb3 is loaded _after_ the nic
interface is brought up, then the deadlock does not occur and thus
fw_supports_fastreg() does indeed need to grab the rtnl lock in that path.

It turns out this code is all useless anyway.  The low level driver will
NOT allow the open if the firmware isn't 7.0, so iw_cxgb3 can always
set the MEM_MGT_EXTENSIONS bit. Simplify...

Signed-off-by: Steve Wise <swise at opengridcomputing.com>
---

 drivers/infiniband/hw/cxgb3/iwch_provider.c |   28 +++------------------------
 1 files changed, 3 insertions(+), 25 deletions(-)

diff --git a/drivers/infiniband/hw/cxgb3/iwch_provider.c b/drivers/infiniband/hw/cxgb3/iwch_provider.c
index b89640a..c8888b8 100644
--- a/drivers/infiniband/hw/cxgb3/iwch_provider.c
+++ b/drivers/infiniband/hw/cxgb3/iwch_provider.c
@@ -1187,28 +1187,6 @@ static ssize_t show_rev(struct device *dev, struct device_attribute *attr,
 	return sprintf(buf, "%d\n", iwch_dev->rdev.t3cdev_p->type);
 }
 
-static int fw_supports_fastreg(struct iwch_dev *iwch_dev)
-{
-	struct ethtool_drvinfo info;
-	struct net_device *lldev = iwch_dev->rdev.t3cdev_p->lldev;
-	char *cp, *next;
-	unsigned fw_maj, fw_min;
-
-	rtnl_lock();
-	lldev->ethtool_ops->get_drvinfo(lldev, &info);
-	rtnl_unlock();
-
-	next = info.fw_version+1;
-	cp = strsep(&next, ".");
-	sscanf(cp, "%i", &fw_maj);
-	cp = strsep(&next, ".");
-	sscanf(cp, "%i", &fw_min);
-
-	PDBG("%s maj %u min %u\n", __func__, fw_maj, fw_min);
-
-	return fw_maj > 6 || (fw_maj == 6 && fw_min > 0);
-}
-
 static ssize_t show_fw_ver(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct iwch_dev *iwch_dev = container_of(dev, struct iwch_dev,
@@ -1325,12 +1303,12 @@ int iwch_register_device(struct iwch_dev *dev)
 	memset(&dev->ibdev.node_guid, 0, sizeof(dev->ibdev.node_guid));
 	memcpy(&dev->ibdev.node_guid, dev->rdev.t3cdev_p->lldev->dev_addr, 6);
 	dev->ibdev.owner = THIS_MODULE;
-	dev->device_cap_flags = IB_DEVICE_LOCAL_DMA_LKEY | IB_DEVICE_MEM_WINDOW;
+	dev->device_cap_flags = IB_DEVICE_LOCAL_DMA_LKEY | 
+				IB_DEVICE_MEM_WINDOW |
+				IB_DEVICE_MEM_MGT_EXTENSIONS;
 
 	/* cxgb3 supports STag 0. */
 	dev->ibdev.local_dma_lkey = 0;
-	if (fw_supports_fastreg(dev))
-		dev->device_cap_flags |= IB_DEVICE_MEM_MGT_EXTENSIONS;
 
 	dev->ibdev.uverbs_cmd_mask =
 	    (1ull << IB_USER_VERBS_CMD_GET_CONTEXT) |