Re: [PATCH] dmaengine: rcar-dmac: Disable interrupts while stopping channels

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On 02-07-18, 17:02, Geert Uytterhoeven wrote:
> During system reboot or halt, with lockdep enabled:
> 
>     ================================
>     WARNING: inconsistent lock state
>     4.18.0-rc1-salvator-x-00002-g9203dbec90a68103 #41 Tainted: G        W
>     --------------------------------
>     inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
>     reboot/2779 [HC0[0]:SC0[0]:HE1:SE1] takes:
>     0000000098ae4ad3 (&(&rchan->lock)->rlock){?.-.}, at: rcar_dmac_shutdown+0x58/0x6c
>     {IN-HARDIRQ-W} state was registered at:
>       lock_acquire+0x208/0x238
>       _raw_spin_lock+0x40/0x54
>       rcar_dmac_isr_channel+0x28/0x200
>       __handle_irq_event_percpu+0x1c0/0x3c8
>       handle_irq_event_percpu+0x34/0x88
>       handle_irq_event+0x48/0x78
>       handle_fasteoi_irq+0xc4/0x12c
>       generic_handle_irq+0x18/0x2c
>       __handle_domain_irq+0xa8/0xac
>       gic_handle_irq+0x78/0xbc
>       el1_irq+0xec/0x1c0
>       arch_cpu_idle+0xe8/0x1bc
>       default_idle_call+0x2c/0x30
>       do_idle+0x144/0x234
>       cpu_startup_entry+0x20/0x24
>       rest_init+0x27c/0x290
>       start_kernel+0x430/0x45c
>     irq event stamp: 12177
>     hardirqs last  enabled at (12177): [<ffffff800881d804>] _raw_spin_unlock_irq+0x2c/0x4c
>     hardirqs last disabled at (12176): [<ffffff800881d638>] _raw_spin_lock_irq+0x1c/0x60
>     softirqs last  enabled at (11948): [<ffffff8008081da8>] __do_softirq+0x160/0x4ec
>     softirqs last disabled at (11935): [<ffffff80080ec948>] irq_exit+0xa0/0xfc
> 
>     other info that might help us debug this:
>      Possible unsafe locking scenario:
> 
> 	   CPU0
> 	   ----
>       lock(&(&rchan->lock)->rlock);
>       <Interrupt>
> 	lock(&(&rchan->lock)->rlock);
> 
>      *** DEADLOCK ***
> 
>     3 locks held by reboot/2779:
>      #0: 00000000bfabfa74 (reboot_mutex){+.+.}, at: sys_reboot+0xdc/0x208
>      #1: 00000000c75d8c3a (&dev->mutex){....}, at: device_shutdown+0xc8/0x1c4
>      #2: 00000000ebec58ec (&dev->mutex){....}, at: device_shutdown+0xd8/0x1c4
> 
>     stack backtrace:
>     CPU: 6 PID: 2779 Comm: reboot Tainted: G        W         4.18.0-rc1-salvator-x-00002-g9203dbec90a68103 #41
>     Hardware name: Renesas Salvator-X 2nd version board based on r8a7795 ES2.0+ (DT)
>     Call trace:
>      dump_backtrace+0x0/0x148
>      show_stack+0x14/0x1c
>      dump_stack+0xb0/0xf0
>      print_usage_bug.part.26+0x1c4/0x27c
>      mark_lock+0x38c/0x610
>      __lock_acquire+0x3fc/0x14d4
>      lock_acquire+0x208/0x238
>      _raw_spin_lock+0x40/0x54
>      rcar_dmac_shutdown+0x58/0x6c
>      platform_drv_shutdown+0x20/0x2c
>      device_shutdown+0x160/0x1c4
>      kernel_restart_prepare+0x34/0x3c
>      kernel_restart+0x14/0x5c
>      sys_reboot+0x160/0x208
>      el0_svc_naked+0x30/0x34
> 
> rcar_dmac_stop_all_chan() takes the channel lock while stopping a
> channel, but does not disable interrupts, leading to a deadlock when a
> DMAC interrupt comes in.  Before, the same code block was called from an
> interrupt handler, hence taking the spinlock was sufficient.
> 
> Fix this by disabling local interrupts while taking the spinlock.

Applied, thanks

-- 
~Vinod
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