On Wed, Aug 13, 2014 at 07:55:26AM -0700, Stephen Boyd wrote: > On 08/13, Russell King - ARM Linux wrote: > > On Wed, Aug 13, 2014 at 06:57:18AM -0700, Stephen Boyd wrote: > > > Commit 1a6b69b6548c (ARM: gic: add CPU migration support, > > > 2012-04-12) introduced an acquisition of the irq_controller_lock > > > in gic_raise_softirq() which can lead to a spinlock recursion if > > > the gic_arch_extn hooks call into the scheduler (via complete() > > > or wake_up(), etc.). This happens because gic_arch_extn hooks are > > > normally called with the irq_controller_lock held and calling > > > into the scheduler may cause us to call smp_send_reschedule() > > > which will grab the irq_controller_lock again. Here's an example > > > from a vendor kernel (note that the gic_arch_extn hook code here > > > isn't actually in mainline): > > > > Here's a question: why would you want to call into the scheduler from > > the gic_arch_extn code? > > In this case we want to send a message to another processor when > an interrupt is enabled that's only a wakeup interrupt in certain > low power states. It's done sort of indirectly, but basically we > block that low power state from being entered so we can ensure > that the interrupt wakes us up from a lighter version of suspend. No, that's not the correct answer for the question I asked. I did not ask "why would you want to call into the IRQ code from the scheduler". I asked "why would you want to call into the scheduler from the gic_arch_extn code?" That's a completely different question. Let me rephrase to try and get an answer to my question: Why are you calling complete() or wake_up() from the gic_arch_extn code? > > static int __disable_irq_nosync(unsigned int irq) > > { > > unsigned long flags; > > struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL); > > We got the lock here. Yes, Daniel pointed that out, which makes this fine of course. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html