[SCSI] BNX2FC: hung task timeout warning observed when rmmod bnx2x with active FCoE...

[v2] - removed the interface->enabled flag setting which prevented the
       fcoe ctlr link from being brought back up after a MTU change

A rtnl_lock deadlock was observed from the rmmod thread where it
tries to unregister the fcoe_ctlr device.  This unregistration
triggered a flush of the sysfs queue of the associated ctlr and led to
a call to the set_fcoe_ctlr_enabled routine.  This will eventually propagate
down to call the bnx2fc_disable routine and contented for the rtnl_lock
in the same context.

This patch creates a subset of the bnx2fc_enable/disable routine which
removes the unnecesary rtnl_lock and the bnx2fc_dev_lock acquisition from
the set_fcoe_ctlr_enabled path.

 kernel: INFO: task rmmod:7874 blocked for more than 120 seconds.
 kernel:      Tainted: G        W  ---------------    2.6.32-415.0.1.el6.x86_64 #1
 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 kernel: rmmod         D 000000000000000f     0  7874   6518 0x00000080
 kernel: ffff88022158f7d8 0000000000000086 0000000000000000 0000000000000000
 kernel: ffff88023fe72600 ffff88043c74d410 ffff88043c74d400 ffff88043c74d000
 kernel: ffff88021ecbe5f8 ffff88022158ffd8 000000000000fbc8 ffff88021ecbe5f8
 kernel: Call Trace:
 kernel: [<ffffffff81525985>] schedule_timeout+0x215/0x2e0
 kernel: [<ffffffff810680c0>] ? pick_next_task_fair+0xd0/0x130
 kernel: [<ffffffff81524858>] ? schedule+0x178/0x3b2
 kernel: [<ffffffff81525603>] wait_for_common+0x123/0x180
 kernel: [<ffffffff81066b40>] ? default_wake_function+0x0/0x20
 kernel: [<ffffffff811a486e>] ? ifind_fast+0x5e/0xb0
 kernel: [<ffffffff8152571d>] wait_for_completion+0x1d/0x20
 kernel: [<ffffffff81203868>] sysfs_addrm_finish+0x228/0x270
 kernel: [<ffffffff812014ab>] sysfs_hash_and_remove+0x5b/0x90
 kernel: [<ffffffff812056af>] sysfs_remove_group+0x5f/0x100
 kernel: [<ffffffff81367e8b>] device_remove_groups+0x3b/0x60
 kernel: [<ffffffff8136811d>] device_remove_attrs+0x3d/0x90
 kernel: [<ffffffff81368295>] device_del+0x125/0x1e0
 kernel: [<ffffffff81368372>] device_unregister+0x22/0x60
 kernel: [<ffffffffa038ead2>] fcoe_ctlr_device_delete+0xe2/0xf4 [libfcoe]
 kernel: [<ffffffffa03c43cb>] bnx2fc_interface_release+0x5b/0x90 [bnx2fc]
 kernel: [<ffffffffa03c4370>] ? bnx2fc_interface_release+0x0/0x90 [bnx2fc]
 kernel: [<ffffffff812835e7>] kref_put+0x37/0x70
 kernel: [<ffffffffa03c4192>] __bnx2fc_destroy+0x72/0xa0 [bnx2fc]
 kernel: [<ffffffffa03c5265>] bnx2fc_ulp_exit+0xf5/0x160 [bnx2fc]    <- got bnx2fc_dev_lock mutex_lock
 kernel: [<ffffffffa03b03c6>] cnic_ulp_exit+0xb6/0xc0 [cnic]
 kernel: [<ffffffffa03b5418>] cnic_netdev_event+0x368/0x370 [cnic]
 kernel: [<ffffffffa038c56c>] ? fcoe_del_netdev_mapping+0x8c/0xa0 [libfcoe]
 kernel: [<ffffffff8152a6e5>] notifier_call_chain+0x55/0x80
 kernel: [<ffffffff810a0a46>] raw_notifier_call_chain+0x16/0x20
 kernel: [<ffffffff81459beb>] call_netdevice_notifiers+0x1b/0x20
 kernel: [<ffffffff8145ab34>] rollback_registered_many+0x154/0x280
 kernel: [<ffffffff8145ad08>] rollback_registered+0x38/0x50
 kernel: [<ffffffff8145ad78>] unregister_netdevice_queue+0x58/0xa0
 kernel: [<ffffffff8145add0>] unregister_netdevice+0x10/0x20
 kernel: [<ffffffff8145adfe>] unregister_netdev+0x1e/0x30                  <- got rtnl_lock!!!!!!!!!
 kernel: [<ffffffffa0122278>] __bnx2x_remove+0x48/0x270 [bnx2x] <- got & rel rtnl_lock
 kernel: [<ffffffffa0122554>] bnx2x_remove_one+0x44/0x80 [bnx2x]
 kernel: [<ffffffff812a3af7>] pci_device_remove+0x37/0x70
 kernel: [<ffffffff8136b2ef>] __device_release_driver+0x6f/0xe0
 kernel: [<ffffffff8136b428>] driver_detach+0xc8/0xd0
 kernel: [<ffffffff8136a22e>] bus_remove_driver+0x8e/0x110
 kernel: [<ffffffff8136bc12>] driver_unregister+0x62/0xa0
 kernel: [<ffffffff812a3e04>] pci_unregister_driver+0x44/0xb0
 kernel: [<ffffffffa0191954>] bnx2x_cleanup+0x18/0x73 [bnx2x]
 kernel: [<ffffffff810b8be4>] sys_delete_module+0x194/0x260
 kernel: [<ffffffff810e1347>] ? audit_syscall_entry+0x1d7/0x200
 kernel: [<ffffffff8100b072>] system_call_fastpath+0x16/0x1b

Signed-off-by: Eddie Wai <eddie.wai@broadcom.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>