linux-kernel - Re: [PATCH v1] mfd: dln2: Run event handler loop under spinlock

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Date:   Mon, 27 Jul 2020 15:03:02 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] mfd: dln2: Run event handler loop under spinlock

On Thu, 23 Jul 2020, Andy Shevchenko wrote:

> The event handler loop must be run with interrupts disabled.
> Otherwise we will have a warning:
> 
> [ 1970.785649] irq 31 handler lineevent_irq_handler+0x0/0x20 enabled interrupts
> [ 1970.792739] WARNING: CPU: 0 PID: 0 at kernel/irq/handle.c:159 __handle_irq_event_percpu+0x162/0x170
> [ 1970.860732] RIP: 0010:__handle_irq_event_percpu+0x162/0x170
> ...
> [ 1970.946994] Call Trace:
> [ 1970.949446]  <IRQ>
> [ 1970.951471]  handle_irq_event_percpu+0x2c/0x80
> [ 1970.955921]  handle_irq_event+0x23/0x43
> [ 1970.959766]  handle_simple_irq+0x57/0x70
> [ 1970.963695]  generic_handle_irq+0x42/0x50
> [ 1970.967717]  dln2_rx+0xc1/0x210 [dln2]
> [ 1970.971479]  ? usb_hcd_unmap_urb_for_dma+0xa6/0x1c0
> [ 1970.976362]  __usb_hcd_giveback_urb+0x77/0xe0
> [ 1970.980727]  usb_giveback_urb_bh+0x8e/0xe0
> [ 1970.984837]  tasklet_action_common.isra.0+0x4a/0xe0
> ...
> 
> Recently xHCI driver switched to tasklets in the commit 36dc01657b49
> ("usb: host: xhci: Support running urb giveback in tasklet context").
> 
> The handle_irq_event_* functions are expected to be called with interrupts
> disabled and they rightfully complain here because we run in tasklet context
> with interrupts enabled.
> 
> Use a event spinlock to protect event handler from being interrupted.
> 
> Note, that there are only two users of this GPIO and ADC drivers and both of
> them are using generic_handle_irq() which makes above happen.
> 
> Fixes: 338a12814297 ("mfd: Add support for Diolan DLN-2 devices")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/mfd/dln2.c | 4 ++++
>  1 file changed, 4 insertions(+)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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