A deadlock trace is seen in netcp driver with lockup detector enabled.
The trace log is provided below for reference. This patch fixes the
bug by removing the usage of netcp_modules_lock within ndo_ops functions.
ndo_{open/close/ioctl)() is already called with rtnl_lock held. So there
is no need to hold another mutex for serialization across processes on
multiple cores.  So remove use of netcp_modules_lock mutex from these
ndo ops functions.

ndo_set_rx_mode() shouldn't be using a mutex as it is called from atomic
context. In the case of ndo_set_rx_mode(), there can be call to this API
without rtnl_lock held from an atomic context. As the underlying modules
are expected to add address to a hardware table, it is to be protected
across concurrent updates and hence a spin lock is used to synchronize
the access. Same with ndo_vlan_rx_add_vid() & ndo_vlan_rx_kill_vid().

Probably the netcp_modules_lock is used to protect the module not being
removed as part of rmmod. Currently this is not fully implemented and
assumes the interface is brought down before doing rmmod of modules.
The support for rmmmod while interface is up is expected in a future
patch set when additional modules such as pa, qos are added. For now
all of the tests such as if up/down, reboot, iperf works fine with this
patch applied.

Deadlock trace seen with lockup detector enabled is shown below for
reference.

[   16.863014] ======================================================
[   16.869183] [ INFO: possible circular locking dependency detected ]
[   16.875441] 4.1.6-01265-gfb1e101 #1 Tainted: G        W
[   16.881176] -------------------------------------------------------
[   16.887432] ifconfig/1662 is trying to acquire lock:
[   16.892386]  (netcp_modules_lock){+.+.+.}, at: [<c03e8110>]
netcp_ndo_open+0x168/0x518
[   16.900321]
[   16.900321] but task is already holding lock:
[   16.906144]  (rtnl_mutex){+.+.+.}, at: [<c053a418>] devinet_ioctl+0xf8/0x7e4
[   16.913206]
[   16.913206] which lock already depends on the new lock.
[   16.913206]
[   16.921372]
[   16.921372] the existing dependency chain (in reverse order) is:
[   16.928844]
-> #1 (rtnl_mutex){+.+.+.}:
[   16.932865]        [<c06023f0>] mutex_lock_nested+0x68/0x4a8
[   16.938521]        [<c04c5758>] register_netdev+0xc/0x24
[   16.943831]        [<c03e65c0>] netcp_module_probe+0x214/0x2ec
[   16.949660]        [<c03e8a54>] netcp_register_module+0xd4/0x140
[   16.955663]        [<c089654c>] keystone_gbe_init+0x10/0x28
[   16.961233]        [<c000977c>] do_one_initcall+0xb8/0x1f8
[   16.966714]        [<c0867e04>] kernel_init_freeable+0x148/0x1e8
[   16.972720]        [<c05f9994>] kernel_init+0xc/0xe8
[   16.977682]        [<c0010038>] ret_from_fork+0x14/0x3c
[   16.982905]
-> #0 (netcp_modules_lock){+.+.+.}:
[   16.987619]        [<c006eab0>] lock_acquire+0x118/0x320
[   16.992928]        [<c06023f0>] mutex_lock_nested+0x68/0x4a8
[   16.998582]        [<c03e8110>] netcp_ndo_open+0x168/0x518
[   17.004064]        [<c04c48f0>] __dev_open+0xa8/0x10c
[   17.009112]        [<c04c4b74>] __dev_change_flags+0x94/0x144
[   17.014853]        [<c04c4c3c>] dev_change_flags+0x18/0x48
[   17.020334]        [<c053a9fc>] devinet_ioctl+0x6dc/0x7e4
[   17.025729]        [<c04a59ec>] sock_ioctl+0x1d0/0x2a8
[   17.030865]        [<c0142844>] do_vfs_ioctl+0x41c/0x688
[   17.036173]        [<c0142ae4>] SyS_ioctl+0x34/0x5c
[   17.041046]        [<c000ff60>] ret_fast_syscall+0x0/0x54
[   17.046441]
[   17.046441] other info that might help us debug this:
[   17.046441]
[   17.054434]  Possible unsafe locking scenario:
[   17.054434]
[   17.060343]        CPU0                    CPU1
[   17.064862]        ----                    ----
[   17.069381]   lock(rtnl_mutex);
[   17.072522]                                lock(netcp_modules_lock);
[   17.078875]                                lock(rtnl_mutex);
[   17.084532]   lock(netcp_modules_lock);
[   17.088366]
[   17.088366]  *** DEADLOCK ***
[   17.088366]
[   17.094279] 1 lock held by ifconfig/1662:
[   17.098278]  #0:  (rtnl_mutex){+.+.+.}, at: [<c053a418>]
devinet_ioctl+0xf8/0x7e4
[   17.105774]
[   17.105774] stack backtrace:
[   17.110124] CPU: 1 PID: 1662 Comm: ifconfig Tainted: G        W
4.1.6-01265-gfb1e101 #1
[   17.118637] Hardware name: Keystone
[   17.122123] [<c00178e4>] (unwind_backtrace) from [<c0013cbc>]
(show_stack+0x10/0x14)
[   17.129862] [<c0013cbc>] (show_stack) from [<c05ff450>]
(dump_stack+0x84/0xc4)
[   17.137079] [<c05ff450>] (dump_stack) from [<c0068e34>]
(print_circular_bug+0x210/0x330)
[   17.145161] [<c0068e34>] (print_circular_bug) from [<c006ab7c>]
(validate_chain.isra.35+0xf98/0x13ac)
[   17.154372] [<c006ab7c>] (validate_chain.isra.35) from [<c006da60>]
(__lock_acquire+0x52c/0xcc0)
[   17.163149] [<c006da60>] (__lock_acquire) from [<c006eab0>]
(lock_acquire+0x118/0x320)
[   17.171058] [<c006eab0>] (lock_acquire) from [<c06023f0>]
(mutex_lock_nested+0x68/0x4a8)
[   17.179140] [<c06023f0>] (mutex_lock_nested) from [<c03e8110>]
(netcp_ndo_open+0x168/0x518)
[   17.187484] [<c03e8110>] (netcp_ndo_open) from [<c04c48f0>]
(__dev_open+0xa8/0x10c)
[   17.195133] [<c04c48f0>] (__dev_open) from [<c04c4b74>]
(__dev_change_flags+0x94/0x144)
[   17.203129] [<c04c4b74>] (__dev_change_flags) from [<c04c4c3c>]
(dev_change_flags+0x18/0x48)
[   17.211560] [<c04c4c3c>] (dev_change_flags) from [<c053a9fc>]
(devinet_ioctl+0x6dc/0x7e4)
[   17.219729] [<c053a9fc>] (devinet_ioctl) from [<c04a59ec>]
(sock_ioctl+0x1d0/0x2a8)
[   17.227378] [<c04a59ec>] (sock_ioctl) from [<c0142844>]
(do_vfs_ioctl+0x41c/0x688)
[   17.234939] [<c0142844>] (do_vfs_ioctl) from [<c0142ae4>]
(SyS_ioctl+0x34/0x5c)
[   17.242242] [<c0142ae4>] (SyS_ioctl) from [<c000ff60>]
(ret_fast_syscall+0x0/0x54)
[   17.258855] netcp-1.0 2620110.netcp eth0: Link is Up - 1Gbps/Full - flow
control off
[   17.271282] BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:616
[   17.279712] in_atomic(): 1, irqs_disabled(): 0, pid: 1662, name: ifconfig
[   17.286500] INFO: lockdep is turned off.
[   17.290413] Preemption disabled at:[<  (null)>]   (null)
[   17.295728]
[   17.297214] CPU: 1 PID: 1662 Comm: ifconfig Tainted: G        W
4.1.6-01265-gfb1e101 #1
[   17.305735] Hardware name: Keystone
[   17.309223] [<c00178e4>] (unwind_backtrace) from [<c0013cbc>]
(show_stack+0x10/0x14)
[   17.316970] [<c0013cbc>] (show_stack) from [<c05ff450>]
(dump_stack+0x84/0xc4)
[   17.324194] [<c05ff450>] (dump_stack) from [<c06023b0>]
(mutex_lock_nested+0x28/0x4a8)
[   17.332112] [<c06023b0>] (mutex_lock_nested) from [<c03e9840>]
(netcp_set_rx_mode+0x160/0x210)
[   17.340724] [<c03e9840>] (netcp_set_rx_mode) from [<c04c483c>]
(dev_set_rx_mode+0x1c/0x28)
[   17.348982] [<c04c483c>] (dev_set_rx_mode) from [<c04c490c>]
(__dev_open+0xc4/0x10c)
[   17.356724] [<c04c490c>] (__dev_open) from [<c04c4b74>]
(__dev_change_flags+0x94/0x144)
[   17.364729] [<c04c4b74>] (__dev_change_flags) from [<c04c4c3c>]
(dev_change_flags+0x18/0x48)
[   17.373166] [<c04c4c3c>] (dev_change_flags) from [<c053a9fc>]
(devinet_ioctl+0x6dc/0x7e4)
[   17.381344] [<c053a9fc>] (devinet_ioctl) from [<c04a59ec>]
(sock_ioctl+0x1d0/0x2a8)
[   17.388994] [<c04a59ec>] (sock_ioctl) from [<c0142844>]
(do_vfs_ioctl+0x41c/0x688)
[   17.396563] [<c0142844>] (do_vfs_ioctl) from [<c0142ae4>]
(SyS_ioctl+0x34/0x5c)
[   17.403873] [<c0142ae4>] (SyS_ioctl) from [<c000ff60>]
(ret_fast_syscall+0x0/0x54)
[   17.413772] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
udhcpc (v1.20.2) started
Sending discover...
[   18.690666] netcp-1.0 2620110.netcp eth0: Link is Up - 1Gbps/Full - flow
control off
Sending discover...
[   22.250972] netcp-1.0 2620110.netcp eth0: Link is Up - 1Gbps/Full - flow
control off
[   22.258721] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   22.265458] BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:616
[   22.273896] in_atomic(): 1, irqs_disabled(): 0, pid: 342, name: kworker/1:1
[   22.280854] INFO: lockdep is turned off.
[   22.284767] Preemption disabled at:[<  (null)>]   (null)
[   22.290074]
[   22.291568] CPU: 1 PID: 342 Comm: kworker/1:1 Tainted: G        W
4.1.6-01265-gfb1e101 #1
[   22.300255] Hardware name: Keystone
[   22.303750] Workqueue: ipv6_addrconf addrconf_dad_work
[   22.308895] [<c00178e4>] (unwind_backtrace) from [<c0013cbc>]
(show_stack+0x10/0x14)
[   22.316643] [<c0013cbc>] (show_stack) from [<c05ff450>]
(dump_stack+0x84/0xc4)
[   22.323867] [<c05ff450>] (dump_stack) from [<c06023b0>]
(mutex_lock_nested+0x28/0x4a8)
[   22.331786] [<c06023b0>] (mutex_lock_nested) from [<c03e9840>]
(netcp_set_rx_mode+0x160/0x210)
[   22.340394] [<c03e9840>] (netcp_set_rx_mode) from [<c04c9d18>]
(__dev_mc_add+0x54/0x68)
[   22.348401] [<c04c9d18>] (__dev_mc_add) from [<c05ab358>]
(igmp6_group_added+0x168/0x1b4)
[   22.356580] [<c05ab358>] (igmp6_group_added) from [<c05ad2cc>]
(ipv6_dev_mc_inc+0x4f0/0x5a8)
[   22.365019] [<c05ad2cc>] (ipv6_dev_mc_inc) from [<c058f0d0>]
(addrconf_dad_work+0x21c/0x33c)
[   22.373460] [<c058f0d0>] (addrconf_dad_work) from [<c0042850>]
(process_one_work+0x214/0x8d0)
[   22.381986] [<c0042850>] (process_one_work) from [<c0042f54>]
(worker_thread+0x48/0x4bc)
[   22.390071] [<c0042f54>] (worker_thread) from [<c004868c>]
(kthread+0xf0/0x108)
[   22.397381] [<c004868c>] (kthread) from [<c0010038>]

Trace related to incorrect usage of mutex inside ndo_set_rx_mode

[   24.086066] BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:616
[   24.094506] in_atomic(): 1, irqs_disabled(): 0, pid: 1682, name: ifconfig
[   24.101291] INFO: lockdep is turned off.
[   24.105203] Preemption disabled at:[<  (null)>]   (null)
[   24.110511]
[   24.112005] CPU: 2 PID: 1682 Comm: ifconfig Tainted: G        W
4.1.6-01265-gfb1e101 #1
[   24.120518] Hardware name: Keystone
[   24.124018] [<c00178e4>] (unwind_backtrace) from [<c0013cbc>]
(show_stack+0x10/0x14)
[   24.131772] [<c0013cbc>] (show_stack) from [<c05ff450>]
(dump_stack+0x84/0xc4)
[   24.138989] [<c05ff450>] (dump_stack) from [<c06023b0>]
(mutex_lock_nested+0x28/0x4a8)
[   24.146908] [<c06023b0>] (mutex_lock_nested) from [<c03e9840>]
(netcp_set_rx_mode+0x160/0x210)
[   24.155523] [<c03e9840>] (netcp_set_rx_mode) from [<c04c483c>]
(dev_set_rx_mode+0x1c/0x28)
[   24.163787] [<c04c483c>] (dev_set_rx_mode) from [<c04c490c>]
(__dev_open+0xc4/0x10c)
[   24.171531] [<c04c490c>] (__dev_open) from [<c04c4b74>]
(__dev_change_flags+0x94/0x144)
[   24.179528] [<c04c4b74>] (__dev_change_flags) from [<c04c4c3c>]
(dev_change_flags+0x18/0x48)
[   24.187966] [<c04c4c3c>] (dev_change_flags) from [<c053a9fc>]
(devinet_ioctl+0x6dc/0x7e4)
[   24.196145] [<c053a9fc>] (devinet_ioctl) from [<c04a59ec>]
(sock_ioctl+0x1d0/0x2a8)
[   24.203803] [<c04a59ec>] (sock_ioctl) from [<c0142844>]
(do_vfs_ioctl+0x41c/0x688)
[   24.211373] [<c0142844>] (do_vfs_ioctl) from [<c0142ae4>]
(SyS_ioctl+0x34/0x5c)
[   24.218676] [<c0142ae4>] (SyS_ioctl) from [<c000ff60>]
(ret_fast_syscall+0x0/0x54)
[   24.227156] IPv6: ADDRCONF(NETDEV_UP): eth1: link is not ready
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>