On 21/07/2015 05:15, Vinod Koul wrote:
On Mon, Jul 20, 2015 at 10:28:14AM +0200, Julia Lawall wrote:
On Mon, 20 Jul 2015, Alex Smith wrote:
On 19/07/2015 10:08, Julia Lawall wrote:
The file drivers/dma/dma-jz4780.c has a probe function that sets up irqs
using devm_request_irq. The probe function then ends with:
err_unregister_dev:
dma_async_device_unregister(dd);
err_disable_clk:
clk_disable_unprepare(jzdma->clk);
return ret;
}
The remove function, on the other hand contains:
of_dma_controller_free(pdev->dev.of_node);
devm_free_irq(&pdev->dev, jzdma->irq, jzdma);
dma_async_device_unregister(&jzdma->dma_device);
The need for calling devm_free_irq explicitly would be that it needs to
occur before dma_async_device_unregister, to eg avoid a reference to a
dangling pointer. But devm_free_irq is implicitly called after the call
to dma_async_device_unregister at the end of the probe function. Which
one is correct?
Not just users but from a device management you are ensuring that your
device is not able to send any more interrupts and also your tasklet is not
spawned further. For this it is neccessary that devm_irq_free be called
explcitly by devices
julia
Hi,
I think the explicit devm_free_irq() here is unnecessary, as when remove is
called there should be no remaining users of the DMA controller and therefore
no chance of an IRQ occurring between the controller being unregistered and an
implicit IRQ release afterwards.
Are you ensuring that device can no longer sent interrupts and all instances
of tasklet running or either completed are terminated and no further tasklet
can be spawned?
Hi Vinod,
If I understand correctly, when remove() is called, there should be no
more users of the DMA controller, enforced by the module reference count.
Wouldn't that guarantee that there are no more transactions running and
therefore no chance of an interrupt from the controller or a tasklet
still running?
Thanks,
Alex
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