Re: lockdep and threaded IRQs

Stefan Richter
2009-02-28T11:49:32Z

David Brownell wrote:
> Now, where is that being set up as being threaded? I
> referenced that a message or two earlier:
>
> drivers/mfd/twl4030-irq.c
>
> Where you'll observe twl_init_irq() at line 688 setting
> up the thread and the Primary IRQ Handler (PIH) dispatch.
> That's pretty much bog-standard chained IRQ setup code,
> except that it chains through a thread.
>
> When an IRQ comes in, handle_twl4030_pih() acks and masks
> that top level IRQ. Then it wakes twl4030_irq_thread(),
> which issues I2C operations to read the IRQ status from
> the chip ... first PIH to find out which SIH modules are
> raising an IRQ, then SIH to dispatch that status. Then
> handle_irq() from that thread to invoke the handler in
> that thread context; it will issue more I2C ops.
>
> And the lockdep thing kicks in through handle_irq(),
> where the IRQ handler wrongly gets invoked with the
> IRQs disabled -- iff lockdep is enabled. Otherwise,
> that IRQ thread is just like any other thread.

Ah, so there /is/ a threaded IRQ handler implementation in the mainline,
down in some driver framework...

Why don't these drivers simply use <linux/workqueue.h>?
--
Stefan Richter
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