This patch prevents the arcnet driver from the following deadlock.

[   41.273910] ======================================================
[   41.280397] [ INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected ]
[   41.287433] 4.4.0-00034-gc0ae784 #536 Not tainted
[   41.292366] ------------------------------------------------------
[   41.298863] arcecho/233 [HC0[0]:SC0[2]:HE0:SE0] is trying to acquire:
[   41.305628]  (&(&lp->lock)->rlock){+.+...}, at: [<bf083bc8>] arcnet_send_packet+0x60/0x1c0 [arcnet]
[   41.315199]
[   41.315199] and this task is already holding:
[   41.321324]  (_xmit_ARCNET#2){+.-...}, at: [<c06b934c>] packet_direct_xmit+0xfc/0x1c8
[   41.329593] which would create a new lock dependency:
[   41.334893]  (_xmit_ARCNET#2){+.-...} -> (&(&lp->lock)->rlock){+.+...}
[   41.341801]
[   41.341801] but this new dependency connects a SOFTIRQ-irq-safe lock:
[   41.350108]  (_xmit_ARCNET#2){+.-...}
... which became SOFTIRQ-irq-safe at:
[   41.357539]   [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.362677]   [<c063ab8c>] dev_watchdog+0x5c/0x264
[   41.367723]   [<c0094edc>] call_timer_fn+0x6c/0xf4
[   41.372759]   [<c00950b8>] run_timer_softirq+0x154/0x210
[   41.378340]   [<c0036b30>] __do_softirq+0x144/0x298
[   41.383469]   [<c0036fb4>] irq_exit+0xcc/0x130
[   41.388138]   [<c0085c50>] __handle_domain_irq+0x60/0xb4
[   41.393728]   [<c0014578>] __irq_svc+0x58/0x78
[   41.398402]   [<c0010274>] arch_cpu_idle+0x24/0x3c
[   41.403443]   [<c007127c>] cpu_startup_entry+0x1f8/0x25c
[   41.409029]   [<c09adc90>] start_kernel+0x3c0/0x3cc
[   41.414170]
[   41.414170] to a SOFTIRQ-irq-unsafe lock:
[   41.419931]  (&(&lp->lock)->rlock){+.+...}
... which became SOFTIRQ-irq-unsafe at:
[   41.427996] ...  [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.433409]   [<bf083d54>] arcnet_interrupt+0x2c/0x800 [arcnet]
[   41.439646]   [<c0089120>] handle_nested_irq+0x8c/0xec
[   41.445063]   [<c03c1170>] regmap_irq_thread+0x190/0x314
[   41.450661]   [<c0087244>] irq_thread_fn+0x1c/0x34
[   41.455700]   [<c0087548>] irq_thread+0x13c/0x1dc
[   41.460649]   [<c0050f10>] kthread+0xe4/0xf8
[   41.465158]   [<c000f810>] ret_from_fork+0x14/0x24
[   41.470207]
[   41.470207] other info that might help us debug this:
[   41.470207]
[   41.478627]  Possible interrupt unsafe locking scenario:
[   41.478627]
[   41.485763]        CPU0                    CPU1
[   41.490521]        ----                    ----
[   41.495279]   lock(&(&lp->lock)->rlock);
[   41.499414]                                local_irq_disable();
[   41.505636]                                lock(_xmit_ARCNET#2);
[   41.511967]                                lock(&(&lp->lock)->rlock);
[   41.518741]   <Interrupt>
[   41.521490]     lock(_xmit_ARCNET#2);
[   41.525356]
[   41.525356]  *** DEADLOCK ***
[   41.525356]
[   41.531587] 1 lock held by arcecho/233:
[   41.535617]  #0:  (_xmit_ARCNET#2){+.-...}, at: [<c06b934c>] packet_direct_xmit+0xfc/0x1c8
[   41.544355]
the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
[   41.552362] -> (_xmit_ARCNET#2){+.-...} ops: 27 {
[   41.557357]    HARDIRQ-ON-W at:
[   41.560664]                     [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.567445]                     [<c063ba28>] dev_deactivate_many+0x114/0x304
[   41.574866]                     [<c063bc3c>] dev_deactivate+0x24/0x38
[   41.581646]                     [<c0630374>] linkwatch_do_dev+0x40/0x74
[   41.588613]                     [<c06305d8>] __linkwatch_run_queue+0xec/0x140
[   41.596120]                     [<c0630658>] linkwatch_event+0x2c/0x34
[   41.602991]                     [<c004af30>] process_one_work+0x188/0x40c
[   41.610131]                     [<c004b200>] worker_thread+0x4c/0x480
[   41.616912]                     [<c0050f10>] kthread+0xe4/0xf8
[   41.623048]                     [<c000f810>] ret_from_fork+0x14/0x24
[   41.629735]    IN-SOFTIRQ-W at:
[   41.633039]                     [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.639820]                     [<c063ab8c>] dev_watchdog+0x5c/0x264
[   41.646508]                     [<c0094edc>] call_timer_fn+0x6c/0xf4
[   41.653190]                     [<c00950b8>] run_timer_softirq+0x154/0x210
[   41.660425]                     [<c0036b30>] __do_softirq+0x144/0x298
[   41.667201]                     [<c0036fb4>] irq_exit+0xcc/0x130
[   41.673518]                     [<c0085c50>] __handle_domain_irq+0x60/0xb4
[   41.680754]                     [<c0014578>] __irq_svc+0x58/0x78
[   41.687077]                     [<c0010274>] arch_cpu_idle+0x24/0x3c
[   41.693769]                     [<c007127c>] cpu_startup_entry+0x1f8/0x25c
[   41.701006]                     [<c09adc90>] start_kernel+0x3c0/0x3cc
[   41.707791]    INITIAL USE at:
[   41.711003]                    [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.717696]                    [<c063ba28>] dev_deactivate_many+0x114/0x304
[   41.725026]                    [<c063bc3c>] dev_deactivate+0x24/0x38
[   41.731718]                    [<c0630374>] linkwatch_do_dev+0x40/0x74
[   41.738593]                    [<c06305d8>] __linkwatch_run_queue+0xec/0x140
[   41.746011]                    [<c0630658>] linkwatch_event+0x2c/0x34
[   41.752789]                    [<c004af30>] process_one_work+0x188/0x40c
[   41.759847]                    [<c004b200>] worker_thread+0x4c/0x480
[   41.766541]                    [<c0050f10>] kthread+0xe4/0xf8
[   41.772596]                    [<c000f810>] ret_from_fork+0x14/0x24
[   41.779198]  }
[   41.780945]  ... key      at: [<c124d620>] netdev_xmit_lock_key+0x38/0x1c8
[   41.788192]  ... acquired at:
[   41.791309]    [<c007bed8>] lock_acquire+0x70/0x90
[   41.796361]    [<c06f9140>] _raw_spin_lock_irqsave+0x40/0x54
[   41.802324]    [<bf083bc8>] arcnet_send_packet+0x60/0x1c0 [arcnet]
[   41.808844]    [<c06b9380>] packet_direct_xmit+0x130/0x1c8
[   41.814622]    [<c06bc7e4>] packet_sendmsg+0x3b8/0x680
[   41.820034]    [<c05fe8b0>] sock_sendmsg+0x14/0x24
[   41.825091]    [<c05ffd68>] SyS_sendto+0xb8/0xe0
[   41.829956]    [<c05ffda8>] SyS_send+0x18/0x20
[   41.834638]    [<c000f780>] ret_fast_syscall+0x0/0x1c
[   41.839954]
[   41.841514]
the dependencies between the lock to be acquired and SOFTIRQ-irq-unsafe lock:
[   41.850302] -> (&(&lp->lock)->rlock){+.+...} ops: 5 {
[   41.855644]    HARDIRQ-ON-W at:
[   41.858945]                     [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.865726]                     [<bf083d54>] arcnet_interrupt+0x2c/0x800 [arcnet]
[   41.873607]                     [<c0089120>] handle_nested_irq+0x8c/0xec
[   41.880666]                     [<c03c1170>] regmap_irq_thread+0x190/0x314
[   41.887901]                     [<c0087244>] irq_thread_fn+0x1c/0x34
[   41.894593]                     [<c0087548>] irq_thread+0x13c/0x1dc
[   41.901195]                     [<c0050f10>] kthread+0xe4/0xf8
[   41.907338]                     [<c000f810>] ret_from_fork+0x14/0x24
[   41.914025]    SOFTIRQ-ON-W at:
[   41.917328]                     [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.924106]                     [<bf083d54>] arcnet_interrupt+0x2c/0x800 [arcnet]
[   41.931981]                     [<c0089120>] handle_nested_irq+0x8c/0xec
[   41.939028]                     [<c03c1170>] regmap_irq_thread+0x190/0x314
[   41.946264]                     [<c0087244>] irq_thread_fn+0x1c/0x34
[   41.952954]                     [<c0087548>] irq_thread+0x13c/0x1dc
[   41.959548]                     [<c0050f10>] kthread+0xe4/0xf8
[   41.965689]                     [<c000f810>] ret_from_fork+0x14/0x24
[   41.972379]    INITIAL USE at:
[   41.975595]                    [<c06f8fc8>] _raw_spin_lock+0x30/0x40
[   41.982283]                    [<bf083d54>] arcnet_interrupt+0x2c/0x800 [arcnet]
[   41.990063]                    [<c0089120>] handle_nested_irq+0x8c/0xec
[   41.997027]                    [<c03c1170>] regmap_irq_thread+0x190/0x314
[   42.004172]                    [<c0087244>] irq_thread_fn+0x1c/0x34
[   42.010766]                    [<c0087548>] irq_thread+0x13c/0x1dc
[   42.017267]                    [<c0050f10>] kthread+0xe4/0xf8
[   42.023314]                    [<c000f810>] ret_from_fork+0x14/0x24
[   42.029903]  }
[   42.031648]  ... key      at: [<bf0854cc>] __key.42091+0x0/0xfffff0f8 [arcnet]
[   42.039255]  ... acquired at:
[   42.042372]    [<c007bed8>] lock_acquire+0x70/0x90
[   42.047413]    [<c06f9140>] _raw_spin_lock_irqsave+0x40/0x54
[   42.053364]    [<bf083bc8>] arcnet_send_packet+0x60/0x1c0 [arcnet]
[   42.059872]    [<c06b9380>] packet_direct_xmit+0x130/0x1c8
[   42.065634]    [<c06bc7e4>] packet_sendmsg+0x3b8/0x680
[   42.071030]    [<c05fe8b0>] sock_sendmsg+0x14/0x24
[   42.076069]    [<c05ffd68>] SyS_sendto+0xb8/0xe0
[   42.080926]    [<c05ffda8>] SyS_send+0x18/0x20
[   42.085601]    [<c000f780>] ret_fast_syscall+0x0/0x1c
[   42.090918]
[   42.092481]
[   42.092481] stack backtrace:
[   42.097065] CPU: 0 PID: 233 Comm: arcecho Not tainted 4.4.0-00034-gc0ae784 #536
[   42.104751] Hardware name: Generic AM33XX (Flattened Device Tree)
[   42.111183] [<c0017ec8>] (unwind_backtrace) from [<c00139d0>] (show_stack+0x10/0x14)
[   42.119337] [<c00139d0>] (show_stack) from [<c02a82c4>] (dump_stack+0x8c/0x9c)
[   42.126937] [<c02a82c4>] (dump_stack) from [<c0078260>] (check_usage+0x4bc/0x63c)
[   42.134815] [<c0078260>] (check_usage) from [<c0078438>] (check_irq_usage+0x58/0xb0)
[   42.142964] [<c0078438>] (check_irq_usage) from [<c007aaa0>] (__lock_acquire+0x1524/0x20b0)
[   42.151740] [<c007aaa0>] (__lock_acquire) from [<c007bed8>] (lock_acquire+0x70/0x90)
[   42.159886] [<c007bed8>] (lock_acquire) from [<c06f9140>] (_raw_spin_lock_irqsave+0x40/0x54)
[   42.168768] [<c06f9140>] (_raw_spin_lock_irqsave) from [<bf083bc8>] (arcnet_send_packet+0x60/0x1c0 [arcnet])
[   42.179115] [<bf083bc8>] (arcnet_send_packet [arcnet]) from [<c06b9380>] (packet_direct_xmit+0x130/0x1c8)
[   42.189182] [<c06b9380>] (packet_direct_xmit) from [<c06bc7e4>] (packet_sendmsg+0x3b8/0x680)
[   42.198059] [<c06bc7e4>] (packet_sendmsg) from [<c05fe8b0>] (sock_sendmsg+0x14/0x24)
[   42.206199] [<c05fe8b0>] (sock_sendmsg) from [<c05ffd68>] (SyS_sendto+0xb8/0xe0)
[   42.213978] [<c05ffd68>] (SyS_sendto) from [<c05ffda8>] (SyS_send+0x18/0x20)
[   42.221388] [<c05ffda8>] (SyS_send) from [<c000f780>] (ret_fast_syscall+0x0/0x1c)
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

   ---
   v1 -> v2: removed unneeded zero assignment of flags
Signed-off-by: David S. Miller <davem@davemloft.net>