Messages in this thread | | | Date | Sat, 13 Sep 2014 21:12:16 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH/RFC] rtc: rtc-twl: Fixed nested IRQ handling in resume from suspend |
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On Sat, 13 Sep 2014, Laurent Pinchart wrote:
> The TWL RTC interrupt is a double-nested threaded interrupt, handled > through the TWL SIH (Secondary Interrupt Handler) and PIH (Primary > Interrupt Handler). > > When the system is woken up from suspend by a TWL RTC alarm interrupt, > the TWL PIH and SIH are enabled first (due to the normal IRQ enabling > sequence for the PIH and to the IRQF_EARLY_RESUME flag for the SIH) > before the TWL RTC interrupt gets enabled. This results on the interrupt > being processed by the TWL primary interrupt handler, forwarded to the > nested SIH, and then marked as pending for the RTC by handle_nested_irq > called from the SIH. > > The RTC interrupt then eventually gets reenabled the kernel, which will > try to call its top half interrupt handler. As the interrupt is a nested > threaded IRQ, its primary handler has been set to the > irq_nested_primary_handler function, which is never supposed to be > called and generates a WARN_ON, without waking the IRQ thread up. > > Fix this by setting the IRQF_EARLY_RESUME for the TWL RTC interrupt to > ensure it gets enabled before the parent handlers try to process it. > > This is likely a bit of a hack, I have a feeling that a more generic > solution that would fix the problem for all nested threaded IRQs enabled > as a wake up source by enable_irq_wake would be better.
Indeed. It's a hack. This is not the first abuse of IRQF_EARLY_RESUME which is used to "fix" ordering issues with nested thread handlers.
I haven't come around yet to analyze the issue and come up with a proper core side mechanism to handle that case. I put it on the "look at it while trapped in a tin can" list.
Thanks,
tglx
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