Messages in this thread Patch in this message | | | Date | Fri, 27 Feb 2009 21:12:03 -0800 | From | Andrew Morton <> | Subject | Re: lockdep and threaded IRQs (was: ...) |
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On Fri, 27 Feb 2009 20:46:50 -0800 David Brownell <david-b@pacbell.net> wrote:
> 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.
OK, that's clever. I never knew that anyone was doing that. afaict MFD is the only such place...
Yes, it's regrettable that it's a private-to-mfd implementation. I expect a lot of i2c clients (at least) would like this.
> 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.
yup.
> 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.
OK.
Perhaps it would be somewhat less dirty to do something like
--- a/kernel/irq/manage.c~a +++ a/kernel/irq/manage.c @@ -689,7 +689,8 @@ int request_irq(unsigned int irq, irq_ha /* * Lockdep wants atomic interrupt handlers: */ - irqflags |= IRQF_DISABLED; + if (!(irqflags & IRQF_NO_LOCKDEP_HACK)) + irqflags |= IRQF_DISABLED; #endif /* * Sanity-check: shared interrupts must pass in a real dev-ID, _
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